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uniapp-canvas动态画图

作者:互联网

r-canvas.js

 

export default{
    data(){
        return{
            system_info:{}, //system info
            canvas_width:0, //canvas width px
            canvas_height:0, //canvas height px
            ctx:null, //canvas object
            canvas_id:null, //canvas id
            hidden:false,//Whether to hide canvas
            scale:1,//canvas scale
            r_canvas_scale:1,
            if_ctx:true
        }
    },
    methods:{
        /**
         * save r-canvas.vue object
         * @param {Object} that
         */
        // saveThis(that){
        //     rCanvasThis = that
        // },
        /**
         * Draw round rect text
         * @param {Object} config
         * @param {Number} config.x x坐标
         * @param {Number} config.y y坐标
         * @param {Number} config.w 宽度
         * @param {Number} config.h 高度
         * @param {Number} config.radius 圆角弧度
         * @param {String} config.fill_color 矩形颜色
         */
        fillRoundRect(config) {
            return new Promise((resolve,reject)=>{
                let x = this.compatibilitySize(parseFloat(config.x)*this.scale)
                let y = this.compatibilitySize(parseFloat(config.y)*this.scale)
                let w = this.compatibilitySize(parseFloat(config.w)*this.scale)
                let h = this.compatibilitySize(parseFloat(config.h)*this.scale)
                let radius = config.radius?parseFloat(config.radius)*this.scale:10*this.scale
                
                let fill_color = config.fill_color || "black"
                // The diameter of the circle must be less than the width and height of the rectangle
                if (2 * radius > w || 2 * radius > h) { 
                    reject("The diameter of the circle must be less than the width and height of the rectangle")
                    return false; 
                }
                this.ctx.save();
                this.ctx.translate(x, y);
                //  
                this.drawRoundRectPath({
                    w: w, 
                    h: h, 
                    radius: radius
                });
                this.ctx.fillStyle = fill_color
                this.ctx.fill();
                this.ctx.restore();
                resolve()
            })
        },
        /**
         * Draws the sides of a rounded rectangle
         * @param {Object} config
         * @param {Number} config.w 宽度
         * @param {Number} config.h 高度
         * @param {Number} config.radius 圆角弧度
         */
        drawRoundRectPath(config) {
            this.ctx.beginPath(0);
            this.ctx.arc(config.w - config.radius, config.h - config.radius, config.radius, 0, Math.PI / 2);
            this.ctx.lineTo(config.radius, config.h);
            this.ctx.arc(config.radius, config.h - config.radius, config.radius, Math.PI / 2, Math.PI);
            this.ctx.lineTo(0, config.radius);
            this.ctx.arc(config.radius, config.radius, config.radius, Math.PI, Math.PI * 3 / 2);
            this.ctx.lineTo(config.w - config.radius, 0);
            this.ctx.arc(config.w - config.radius, config.radius, config.radius, Math.PI * 3 / 2, Math.PI * 2);
            this.ctx.lineTo(config.w, config.h - config.radius);
            this.ctx.closePath();
        },
        /**
         * Draw special Text,line wrapping is not supported
         * @param {Object} config
         * @param {String} config.text 文字
         * @param {Number} config.x x坐标
         * @param {Number} config.y y坐标
         * @param {String} config.font_color 文字颜色
         * @param {String} config.font_family 文字字体
         * @param {Number} config.font_size 文字大小(px)
         */
        drawSpecialText(config_arr){
            return new Promise(async (resolve,reject)=>{
                if(config_arr && config_arr.length>0){
                    for(let i in config_arr){
                        if(i != 0){
                            for(let a in config_arr){
                                if(a < i){
                                    // 先处理font-size才能知道字体宽度
                                    let font_size = config_arr[a].font_size?parseFloat(config_arr[a].font_size)*this.scale:20*this.scale
                                    this.ctx.setFontSize(this.compatibilitySize(font_size))
                                    config_arr[i].x = parseFloat(config_arr[i].x)*this.scale + this.ctx.measureText(config_arr[a].text).width
                                }else{
                                    break;
                                }
                            }
                        }
                        await this.drawText(config_arr[i])
                    }
                    resolve()
                }else{
                    reject("The length of config arr is less than 0")
                    return;
                }
                
            })
        },
        /**
         * array delete empty
         * @param {Object} arr
         */
        arrDeleteEmpty(arr){
            let newArr = []
            for(let i in arr){
                if(arr[i]){
                    newArr.push(arr[i])
                }
            }
            return newArr
        },
        /**
         * Draw Text,support line
         * @param {Object} config
         * @param {String} config.text 文字
         * @param {Number} config.max_width 文字最大宽度(大于宽度自动换行)
         * @param {Number} config.line_height 文字上下行间距
         * @param {Number} config.x x坐标
         * @param {Number} config.y y坐标
         * @param {String} config.font_color 文字颜色
         * @param {String} config.font_family 文字字体 默认值:Arial
         * @param {String} config.text_align 文字对齐方式(left/center/right)
         * @param {Number} config.font_size 文字大小(px)
         * @param {Boolean} config.line_through_height 中划线大小
         * @param {Boolean} config.line_through_color 中划线颜色
         * @param {String} config.font_style 规定文字样式
         * @param {String} config.font_variant 规定字体变体
         * @param {String} config.font_weight 规定字体粗细
         * @param {String} config.line_through_cap 线末端类型
         * @param {String} config.line_clamp 最大行数
         * @param {String} config.line_clamp_hint 超过line_clamp后,尾部显示的自定义标识 如 ...
         * @param {String} config.is_line_break 是否开启换行符换行
         * 
         */
        drawText(config,configuration = {}){
            
            configuration['line_num'] = configuration.line_num?configuration.line_num:0
            configuration['text_width'] = configuration.text_width?configuration.text_width:0
            
            return new Promise(async (resolve,reject)=>{
                
                if(config.text){
                    
                    let draw_width = 0,draw_height = 0,draw_x = config.x,draw_y = config.y
                    let font_size = config.font_size?(parseFloat(config.font_size)*this.scale):(20*this.scale)
                    let font_color = config.font_color || "#000"
                    let font_family = config.font_family || "Arial"
                    let line_height = config.line_height || config.font_size || 20
                    let text_align = config.text_align || "left"
                    let font_weight = config.font_weight || "normal"
                    let font_variant = config.font_variant || "normal"
                    let font_style = config.font_style || "normal"
                    let line_clamp_hint = config.line_clamp_hint || '...'
                    let lineBreakJoinText = ""
                    let max_width = config.max_width?parseFloat(config.max_width)*this.scale:0
                    // checkout is line break
                    if(config.is_line_break){
                        let splitTextArr = config.text.split(/[\n]/g)
                        if(splitTextArr && splitTextArr.length > 0){
                            let newSplitTextArr = this.arrDeleteEmpty(splitTextArr)
                            if(newSplitTextArr && newSplitTextArr.length > 0){
                                lineBreakJoinText = newSplitTextArr.slice(1).join("\n")
                                config.text = newSplitTextArr[0]
                            }else{
                                reject("Text cannot be empty:103")
                                return
                            }
                        }else{
                            reject("Text cannot be empty:102")
                            return
                        }
                    }
                    
                    this.ctx.setFillStyle(font_color) // color
                    this.ctx.textAlign = text_align;
                    this.ctx.font = `${font_style} ${font_variant} ${font_weight} ${parseInt(font_size)}px ${font_family}`
                    if(configuration.text_width >= this.ctx.measureText(config.text).width){
                        draw_width = configuration.text_width
                    }else if(max_width > 0){
                        draw_width = max_width < this.ctx.measureText(config.text).width ? this.resetCompatibilitySize(max_width) : this.resetCompatibilitySize(this.ctx.measureText(config.text).width)
                    }else{
                        draw_width = this.resetCompatibilitySize(this.ctx.measureText(config.text).width)
                    }
                    configuration.text_width = draw_width
                    if( max_width && this.compatibilitySize(this.ctx.measureText(config.text).width) > this.compatibilitySize(max_width)){
                        let current_text = ""
                        let text_arr = config.text.split("")
                        for(let i in text_arr){
                            if( this.compatibilitySize(this.ctx.measureText(current_text+text_arr[i]).width) > this.compatibilitySize(max_width) ){
                                // Hyphenation that is greater than the drawable width continues to draw
                                if(config.line_clamp && parseInt(config.line_clamp) == 1){
                                    // Subtracting the current_text tail width from the line_clamp_hint width
                                    let current_text_arr = current_text.split('')
                                    let json_current_text = ''
                                    while(true){
                                        current_text_arr = current_text_arr.slice(1)
                                        json_current_text = current_text_arr.join('')
                                        if(this.compatibilitySize(this.ctx.measureText(json_current_text).width) <= this.compatibilitySize(this.ctx.measureText(line_clamp_hint).width)){
                                            current_text = current_text.replace(json_current_text,'')
                                            break;
                                        }
                                    }
                                    configuration.line_num += 1
                                    this.ctx.setFontSize(parseInt(this.compatibilitySize(font_size))) // font size
                                    this.ctx.fillText(current_text + line_clamp_hint, this.compatibilitySize(parseFloat(config.x)*this.scale), this.compatibilitySize(parseFloat(config.y)*this.scale));
                                }else{
                                    configuration.line_num += 1
                                    this.ctx.setFontSize(parseInt(this.compatibilitySize(font_size))) // font size
                                    this.ctx.fillText(current_text, this.compatibilitySize(parseFloat(config.x)*this.scale), this.compatibilitySize(parseFloat(config.y)*this.scale));
                                    config.text = text_arr.slice(i).join("")
                                    config.y = config.y + line_height
                                    if(config.line_clamp){
                                        config.line_clamp = parseInt(config.line_clamp) - 1
                                    }
                                    await this.drawText(config,configuration)
                                }
                                
                                break;
                            }else{
                                current_text = current_text+text_arr[i]
                            }
                        }
                    }else{
                        if(config.line_through_height){
                            let x = parseFloat(config.x)*this.scale
                            let w
                            let y = parseFloat(config.y)*this.scale - (font_size / 2.6) 
                            if(text_align == "left"){
                                w = this.ctx.measureText(config.text).width/1.1 + parseFloat(config.x)*this.scale
                            }else if(text_align == "right"){
                                w = parseFloat(config.x)*this.scale - this.ctx.measureText(config.text).width/1.1
                            }else if(text_align == "center"){
                                x = parseFloat(config.x)*this.scale - this.ctx.measureText(config.text).width / 1.1 / 2
                                w = parseFloat(config.x)*this.scale + this.ctx.measureText(config.text).width / 1.1 / 2
                            }
                            this.drawLineTo({
                                x:x,
                                y:y,
                                w:w,
                                h:y,
                                line_width:config.line_through_height,
                                line_color:config.line_through_color,
                                line_cap:config.line_through_cap
                            })
                        }
                        configuration.line_num += 1
                        this.ctx.setFontSize(parseInt(this.compatibilitySize(font_size))) // font size
                        this.ctx.fillText(config.text, this.compatibilitySize(parseFloat(config.x)*this.scale), this.compatibilitySize(parseFloat(config.y)*this.scale));
                        if(config.line_clamp){
                            config.line_clamp = parseInt(config.line_clamp) - 1
                        }
                    }
                    if(lineBreakJoinText){
                        await this.drawText({...config,text:lineBreakJoinText,y:config.y + line_height},configuration)
                    }
                    draw_height = config.font_size * configuration.line_num
                    draw_width = configuration.text_width
                    resolve({draw_width,draw_height,draw_x,draw_y})
                }else{
                    reject("Text cannot be empty:101")
                }
            })
        },
        /**
         * Draw Line
         * @param {Object} config
         * @param {Object} config.x x坐标
         * @param {Object} config.y y坐标
         * @param {Object} config.w 线的宽度
         * @param {Object} config.h 线的高度
         * @param {Object} config.line_width 线的宽度
         * @param {Object} config.line_color 线条颜色
         */
        drawLineTo(config){
            /**vinn**/
            let y = this.compatibilitySize(config.y)
            let w = this.compatibilitySize(config.w)
            let h = this.compatibilitySize(config.h)
            let line_width = config.line_width?parseFloat(config.line_width)*this.scale:1*this.scale
            let line_color = config.line_color || "black"
            let line_cap = config.line_cap || "butt"
            this.ctx.beginPath()
            this.ctx.lineCap = line_cap
            this.ctx.lineWidth = line_width
            this.ctx.strokeStyle = line_color
            this.ctx.moveTo(x,y)
            this.ctx.lineTo(w,h)
            this.ctx.stroke()
        },
        /** 
         * Compatibility px
         * @param {Object} size
         */
        compatibilitySize(size) {
          let canvasSize = (parseFloat(size) / 750) * this.system_info.windowWidth
          canvasSize = parseFloat(canvasSize * 2)
          return canvasSize
        },
        /**
         * Restore compatibility px
         * @param {Object} size
         */
        resetCompatibilitySize(size) {
          let canvasSize = (parseFloat(size/2)/this.system_info.windowWidth) * 750
          return canvasSize
        },
        /**
         * Init canvas
         */
        init(config){
            return new Promise(async (resolve,reject)=>{
                if(!config.canvas_id){
                    reject("Canvas ID cannot be empty, please refer to the usage example")
                    return;
                }
                this.hidden = config.hidden
                this.canvas_id = config.canvas_id
                let system_info = await uni.getSystemInfoSync()
                this.system_info = system_info
                this.scale = config.scale&&parseFloat(config.scale)>0?parseInt(config.scale):1
                this.canvas_width = (config.canvas_width ? this.compatibilitySize(config.canvas_width) : system_info.windowWidth) * this.scale
                this.canvas_height = (config.canvas_height ? this.compatibilitySize(config.canvas_height) : system_info.windowHeight) * this.scale,
                this.r_canvas_scale = 1/this.scale
                this.ctx = uni.createCanvasContext(this.canvas_id,this)
                this.setCanvasConfig({
                    global_alpha:config.global_alpha?parseFloat(config.global_alpha):1,
                    backgroundColor:config.background_color?config.background_color:"#fff"
                })
                resolve()
            })
        },
        /**
         * clear canvas all path
         */
        clearCanvas(){
            return new Promise(async (resolve,reject)=>{
                if(!this.ctx){
                    reject("canvas is not initialized:101")
                    return
                }else{
                    this.ctx.clearRect(0,0,parseFloat(this.canvas_width)*this.scale,parseFloat(this.canvas_height)*this.scale)
                    await this.draw()
                    resolve()
                }
            })
        },
        /**
         * Set canvas config
         * @param {Object} config
         */
        setCanvasConfig(config){
            this.ctx.globalAlpha = config.global_alpha
            this.ctx.fillStyle = config.backgroundColor
            this.ctx.fillRect(0, 0, parseFloat(this.canvas_width)*this.scale, parseFloat(this.canvas_height)*this.scale)
        },
        /**
         * Draw to filepath
         */
        draw(callback){
            return new Promise((resolve,reject)=>{
                let stop = setTimeout(()=>{
                    this.ctx.draw(false,setTimeout(()=>{
                        uni.canvasToTempFilePath({
                            canvasId: this.canvas_id,
                            quality: 1,
                            destWidth:this.canvas_width,
                            destHeight:this.canvas_height, 
                            success: (res)=>{
                                //console.log('res',res)
                                resolve(res)
                                callback && callback(res)
                            },
                            fail:(err)=>{
                                reject(JSON.stringify(err)|| "Failed to generate poster:101")
                            }
                        },this)
                    },300))
                    clearTimeout(stop)
                },300)
            })
        },
        /**
         * draw rect
         * @param {Number} config.x x坐标
         * @param {Number} config.y y坐标
         * @param {Number} config.w 图形宽度(px)
         * @param {Number} config.h 图形高度(px)
         * @param {Number} config.color 图形颜色
         * @param {Number} config.is_radius 是否开启圆图(1.1.6及以下版本废弃,请使用border_radius)
         * 
         */
        drawRect(config){
            return new Promise(async (resolve,reject)=>{
                let color = config.color || 'white'
                config['color'] = color
                this.ctx.fillStyle = color;
                if(config.is_radius || config.border_radius){
                    this.setNativeBorderRadius(config)
                    this.ctx.fill()
                }else{
                    this.ctx.fillRect(this.compatibilitySize(parseFloat(config.x)*this.scale),this.compatibilitySize(parseFloat(config.y)*this.scale),this.compatibilitySize(parseFloat(config.w)*this.scale),this.compatibilitySize(parseFloat(config.h)*this.scale))
                }
                resolve()
            })
        },
        /**
         * Draw image
         * @param {Object} config
         * @param {String} config.url 图片链接
         * @param {Number} config.x x坐标
         * @param {Number} config.y y坐标
         * @param {Number} config.w 图片宽度(px)
         * @param {Number} config.h 图片高度(px)
         * @param {Number} config.border_width 边大小
         * @param {Number} config.border_color 边颜色
         * @param {Number} config.is_radius 是否开启圆图(1.1.6及以下版本废弃,请使用border_radius)
         * @param {Number} config.border_radius 圆角弧度
         */
        drawImage(config){
            return new Promise(async (resolve,reject)=>{
                if(config.url){
                    let type = 0 // 1、network image  2、native image  3、base64 image
                    let image_url
                    let reg = /^https?/ig;
                    if(reg.test(config.url)){
                        type = 1
                    }else{
                        if((config.url.indexOf("data:image/png;base64") != -1) || config.url.indexOf("data:image/jpeg;base64") != -1){
                            type = 3
                        }else{
                            type = 2
                        }
                    }
                    if(type == 1){
                        // network image
                        await this.downLoadNetworkFile(config.url).then(res=>{ // two function
                            image_url = res
                        }).catch(err=>{
                            reject(err)
                            return;
                        })
                    }else if(type == 2){
                        // native image
                        const imageInfoResult = await uni.getImageInfo({
                            src: config.url
                        });
                        try{
                            if(imageInfoResult.length <= 1){
                                reject(imageInfoResult[0].errMsg + ':404')
                                return
                            }
                        }catch(e){
                            reject(e+':500')
                            return
                        }
                        let base64 = await this.urlToBase64({url:imageInfoResult[1].path})
                        // #ifdef MP-WEIXIN
                        await this.base64ToNative({url:base64}).then(res=>{
                            image_url = res
                        }).catch(err=>{
                            reject(JSON.stringify(err)+":501")
                            return;
                        })
                        // #endif
                        // #ifndef MP-WEIXIN
                        image_url = base64
                        // #endif
                        
                    }else if(type == 3){
                        // #ifdef MP-WEIXIN
                        await this.base64ToNative({url:config.url}).then(res=>{
                            image_url = res
                        }).catch(err=>{
                            reject(JSON.stringify(err)+":500")
                            return;
                        })
                        // #endif
                        // #ifndef MP-WEIXIN
                        image_url = config.url
                        // #endif
                    }else{
                        reject("Other Type Errors:101")
                        return
                    }
                    if(config.border_width){
                        let border_radius = 0
                        if(config.border_radius){
                            let multiple = config.w / config.border_radius
                            border_radius = (parseFloat(config.w) + parseFloat(config.border_width)) / multiple
                        }
                        // drawRect
                        await this.drawRect({
                            x:parseFloat(config.x) - parseFloat(config.border_width)/2,
                            y:parseFloat(config.y) - parseFloat(config.border_width)/2,
                            w:parseFloat(config.w) + parseFloat(config.border_width),
                            h:parseFloat(config.h) + parseFloat(config.border_width),
                            color:config.border_color,
                            border_radius:border_radius,
                            border_width:config.border_width,
                            is_radius:config.is_radius
                        })
                    }
                    
                    

                    if(config.border_radius){
                        this.setNativeBorderRadius(config)
                    }else if(config.is_radius){
                        //已废弃 is_radius
                        this.ctx.setStrokeStyle("rgba(0,0,0,0)")
                        this.ctx.save()
                        this.ctx.beginPath()
                        this.ctx.arc(this.compatibilitySize(parseFloat(config.x)*this.scale+parseFloat(config.w)*this.scale/2), this.compatibilitySize(parseFloat(config.y)*this.scale+parseFloat(config.h)*this.scale/2), this.compatibilitySize(parseFloat(config.w)*this.scale/2), 0, 2 * Math.PI, false)
                        this.ctx.stroke();
                        this.ctx.clip()
                    }
                    
                    await this.ctx.drawImage(image_url,this.compatibilitySize(parseFloat(config.x)*this.scale),this.compatibilitySize(parseFloat(config.y)*this.scale),this.compatibilitySize(parseFloat(config.w)*this.scale),this.compatibilitySize(parseFloat(config.h)*this.scale))
                    this.ctx.restore() //Restore previously saved drawing context
                    resolve()
                }else{
                    let err_msg = "Links cannot be empty:101"
                    reject(err_msg)
                }
            })
        },
        /**
         * base64 to native available path
         * @param {Object} config
         */
        base64ToNative(config){
            return new Promise((resolve,reject)=>{
                let fileName = new Date().getTime()
                var filePath = `${wx.env.USER_DATA_PATH}/${fileName}_rCanvas.png`
                wx.getFileSystemManager().writeFile({
                    filePath: filePath,
                    data: config.url.replace(/^data:\S+\/\S+;base64,/, ''),
                    encoding: 'base64',
                    success: function() {
                        resolve(filePath)
                    },
                    fail: function(error) {
                        reject(error)
                    }
                })
            })
        },
        /**
         * native url to base64
         * @param {Object} config
         */
        urlToBase64(config){
            return new Promise(async (resolve,reject)=>{
                if (typeof window != 'undefined') {
                    await this.downLoadNetworkFile(config.url).then(res=>{ // two function
                        resolve(res)
                    }).catch(err=>{
                        reject(err)
                    })
                }else if (typeof plus != 'undefined') {
                    plus.io.resolveLocalFileSystemURL(config.url,(obj)=>{
                        obj.file((file)=>{
                            let fileReader = new plus.io.FileReader()
                            fileReader.onload = (res)=>{
                                resolve(res.target.result)
                            }
                            fileReader.onerror = (err)=>{
                                reject(err)
                            }
                            fileReader.readAsDataURL(file)
                        }, (err)=>{
                            reject(err)
                        })
                    },(err)=>{
                        reject(err)
                    })
                }else if(typeof wx != 'undefined'){
                    wx.getFileSystemManager().readFile({
                        filePath: config.url,
                        encoding: 'base64',
                        success: function(res) {
                            resolve('data:image/png;base64,' + res.data)
                        },
                        fail: function(error) {
                            reject(error)
                        }
                    })
                }
            })
        },
        setNativeBorderRadius(config){
            let border_radius = config.border_radius?(parseFloat(config.border_radius)*this.scale):(20*this.scale)
            if ((parseFloat(config.w)*this.scale) < 2 * border_radius) border_radius = (parseFloat(config.w)*this.scale) / 2;
            if ((parseFloat(config.h)*this.scale) < 2 * border_radius) border_radius = (parseFloat(config.h)*this.scale) / 2;
            this.ctx.beginPath();
            this.ctx.moveTo(this.compatibilitySize((parseFloat(config.x)*this.scale) + border_radius), this.compatibilitySize((parseFloat(config.y)*this.scale)));
            this.ctx.arcTo(this.compatibilitySize((parseFloat(config.x)*this.scale) + (parseFloat(config.w)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale)), this.compatibilitySize((parseFloat(config.x)*this.scale) + (parseFloat(config.w)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale) + (parseFloat(config.h)*this.scale)), this.compatibilitySize(border_radius));
            this.ctx.arcTo(this.compatibilitySize((parseFloat(config.x)*this.scale) + (parseFloat(config.w)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale) + (parseFloat(config.h)*this.scale)), this.compatibilitySize((parseFloat(config.x)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale) + (parseFloat(config.h)*this.scale)), this.compatibilitySize(border_radius));
            this.ctx.arcTo((this.compatibilitySize(parseFloat(config.x)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale) + (parseFloat(config.h)*this.scale)), this.compatibilitySize((parseFloat(config.x)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale)), this.compatibilitySize(border_radius));
            this.ctx.arcTo(this.compatibilitySize((parseFloat(config.x)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale)), this.compatibilitySize((parseFloat(config.x)*this.scale) + (parseFloat(config.w)*this.scale)), this.compatibilitySize((parseFloat(config.y)*this.scale)), this.compatibilitySize(border_radius));
            this.ctx.closePath();
            this.ctx.strokeStyle = config.color || config.border_color || 'transparent'; // 设置绘制边框的颜色
            this.ctx.stroke();
            this.ctx.save()
            this.ctx.clip();
        },
        /**
         * Download network file
         * @param {Object} url : download url
         */
        downLoadNetworkFile(url){
            return new Promise((resolve,reject)=>{
                uni.downloadFile({
                    url,
                    success:(res)=>{
                        if(res.statusCode == 200){
                            resolve(res.tempFilePath)
                        }else{
                            reject("Download Image Fail:102")
                        }
                    },
                    fail:(err)=>{
                        reject("Download Image Fail:101")
                    }
                })
            })
        },
        /**
         * Save image to natice
         * @param {Object} filePath : native imageUrl
         */
        saveImage(filePath){
            return new Promise((resolve,reject)=>{
                if(!filePath){
                    reject("FilePath cannot be null:101")
                    return;
                }
                
                // #ifdef H5
                    var createA = document.createElement("a");
                    createA.download = filePath;
                    createA.href = filePath;
                    document.body.appendChild(createA);
                    createA.click();
                    createA.remove();
                    resolve()
                // #endif
                
                // #ifndef H5
                uni.saveImageToPhotosAlbum({
                    filePath: filePath,
                    success:(res)=>{
                        resolve(res)
                    }, 
                    fail:(err)=>{
                        reject(err)
                    }
                })
                // #endif
            })
        }
    }
}

 

r-canvas.vue

 

<template>
    <view>
        <view class="r-canvas-component" :style="{width:canvas_width/scale+'px',height:canvas_height/scale+'px'}" :class="{'hidden':hidden}">
            <canvas class="r-canvas" v-if="canvas_id" :canvas-id="canvas_id" :id="canvas_id" :style="{width:canvas_width+'px',height:canvas_height+'px','transform': `scale(${r_canvas_scale})`}"></canvas>
        </view>
    </view>
</template>

<script>
    import rCanvasJS from "./r-canvas.js"
    export default {
        mixins:[rCanvasJS]
    }
</script>
<style>
.r-canvas{
    transform-origin: 0 0;
}
.r-canvas-component{
    overflow: hidden;
}
.r-canvas-component.hidden{
    position: fixed;
    top:-5000upx;
}
</style>

 

页面引用

 

<r-canvas ref="rCanvas"></r-canvas>

 

<script>
const scale = uni.getSystemInfoSync().windowWidth / 750
import rCanvas from '@/components/r-canvas/r-canvas.vue';
export default {
    components: {
        rCanvas
    },
    data() {
        return {
            showPop: false,
            showMDM: false,
            tempFilePath: '',
            tempFilePathwx: '',
            miniProgramCodeFile: '',
            pyqImageUrl: '',
            wxImageUrl: '',
        };
    },
    onl oad() {
    },
    methods: {
        drawCanvas(type) {
            let _this = this;
            uni.showLoading();
            _this.$nextTick(async () => {
                // 初始化
                await _this.$refs.rCanvas.init({
                    canvas_id: 'rCanvas',
                    canvas_width: 290,
                    canvas_height: 385,
                    scale: 2,
                    background_color: 'rgba(0,0,0,0)',
                    hidden: true
                });
                //画图
                await _this.$refs.rCanvas.drawImage({
                    url: 'https://www.dianfz.com/img/poster/fanli/bg_hb_12@2x.png',
                    x: 0,
                    y: 0,
                    w: 290,
                    h: 385
                });
                
                //画图
                await _this.$refs.rCanvas.drawImage({
                    url: _this.miniProgramCodeFile,
                    x: 208,
                    y: 42, 
                    w: 40,
                    h: 40,
                    border_radius: 40
                }); 
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: '新用户买单',
                    max_width: 0,
                    x: 125,
                    y: 136,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: '返现比例:'+_this.detailData.newUDiscount,
                    max_width: 0,
                    x: 125,
                    y: 164,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: '老用户买单',
                    max_width: 0,
                    x: 125,
                    y: 205,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: '返现比例:'+_this.detailData.discount,
                    max_width: 0,
                    x: 125,
                    y: 233,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                if(_this.tiaojian){
                    // 画文字
                     _this.$refs.rCanvas.drawText({
                        text: '推荐'+_this.tiaojian+'人后买单',
                        max_width: 0,
                        x: 115,
                        y: 275,
                        font_color: '#FFFFFF',
                        font_size: 8
                    });
                    // 画文字
                     _this.$refs.rCanvas.drawText({
                        text: '返现比例:'+_this.bili,
                        max_width: 0,
                        x: 125,
                        y: 301,
                        font_color: '#FFFFFF',
                        font_size: 8
                    });
                }
                
                //画图
                await _this.$refs.rCanvas.drawImage({
                    url: _this.storeData.dppicture,
                    x: 18,
                    y: 345,
                    w: 22,
                    h: 16
                });
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: _this.storeData.storeName,
                    max_width: 0,
                    x: 45,
                    y: 350,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                // 画文字
                 _this.$refs.rCanvas.drawText({
                    text: _this.storeData.addressq + _this.storeData.address,
                    max_width: 0,
                    x: 45,
                    y: 361,
                    font_color: '#FFFFFF',
                    font_size: 8
                });
                
                
                // 生成海报
                 _this.$refs.rCanvas.draw(res => {
                    let tmpTimeout = setTimeout(() => {
                        uni.hideLoading();
                        _this.tempFilePath = res.tempFilePath;
                        if(type=='pyq'){
                            _this.pyqShare();
                        }
                        if(type=='mdm'){
                            _this.showMDM = true;
                            _this.showPop = false;
                        }
                        
                        clearTimeout(tmpTimeout);
                    }, 500);
                });
            });
        },
        wxShare() {
            let _this = this;if (_this.tempFilePathwx) {
                uni.share({
                    provider: 'weixin',
                    scene: 'WXSceneSession',
                    type: 5,
                    title: '【'+_this.storeData.storeName+'】送你会员权益,买必返,最高返现'+sbili+'%.',
                    imageUrl:_this.tempFilePathwx,
                    miniProgram: {
                        id: _this.$wechatAppId, 
                        type: _this.$wechatVersion,
                        path: 'pages/share/VIP/dtl?id=' + _this.detailData.id,
                        webUrl: 'http://www.dianfz.com'
                    },
                    success: function(res) {
                        console.log(res);
                    },
                    fail: function(err) {
                        uni.showModal({
                            content: err.errMsg
                        });
                    }
                });
            } else {
                _this.drawCanvaswx('wx');
            }
        },
    }
};
</script>

 

标签:uniapp,canvas,scale,ctx,画图,param,width,parseFloat,config
来源: https://www.cnblogs.com/vinn7/p/16373072.html