canvas 识别图片颜色 解析图片颜色

摘要：在线预览方法传入坐标点，获取坐标点的颜色值返回对象解析完成之后返回图片的颜色列表属性解析图像时的进度百分比解析图像颜色时的精度方法引入库实例代码上传图片之后替换图片执行方法获取图片，实例化图片执行方法解析完成，获得数组，操作回调函数获取坐标

在线 预览 http://jsrun.net/DjkKp/edit
github  https://github.com/Taoqun/can...

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方法

getColorXY(x,y) 传入坐标点，获取坐标点的颜色值

getColors() 返回 promise 对象 解析完成之后返回图片的颜色列表

属性

progress String 解析图像时的进度 百分比

accuracy Number 解析图像颜色时的精度

html

js方法

// 引入canvas_get_image_colors库
// 实例代码

let input = document.querySelector("#file")

input.addEventListener("change", (event) => {
    /**
     * 上传图片之后
     * 替换图片
     * 执行方法
     */
    let img = document.querySelector("#img")
    let file = event.target.files[0]
    let fr = new FileReader() 

    fr.onload = (e) => {
        let n_img = new Image()
        n_img.src = e.target.result
        n_img.onload = (e) => {
            n_img.id = "img"
            n_img.width = n_img.width
            n_img.height = n_img.height
            document.body.replaceChild(n_img, img)
            getImg()
        }
    }

    fr.readAsDataURL(file)
})

function getImg() {
    /**
     * 获取图片，实例化图片
     * 执行方法
     * 解析完成，获得数组，操作回调函数
     * 
     */
    let img = document.querySelector("#img")
    let a = new getImgColor(img)
    
    // 获取 坐标 0 0 点的颜色值
    console.log(a.getColorXY(0, 0))

    a.getColors().then((arr) => {

        let ul = document.querySelector("#ul")
        let text = document.querySelector("#text")
            text.innerText = "共有" + arr.length + "个颜色";
        let str = ""

        arr.forEach((obj, index) => {
            str += `
${obj["#"]} - ${obj["index"]}次
`;
        })

        ul.innerHTML = str
    })
}

canvas_get_image_colors.js库

// 封装函数库
function getImgColor(img) {
    /**
     * @ param 传入的图片 
     * @ this.progress 解析图片的进度 实时
     * @ this.canvas canvas元素
     * @ this.cvs context对象
     * @ this.accuracy Number 解析图片颜色的精确度 1 - 7 数字选择 
     *
     * 
     * @ anther taoqun 
     */

    this.canvas = document.createElement("canvas")
    this.canvas.width = img.width
    this.canvas.height = img.height
    this.cvs = this.canvas.getContext("2d")
    this.cvs.drawImage(img, 0, 0)
    this.accuracy = 5
    this.progress = ""
}
getImgColor.prototype.getColorXY = function(x, y) {

    /**
     * @param x Number x坐标起点
     * @param y Number y坐标起点
     * @return color Object 包含颜色的rgba #16进制颜色
     */

    let obj = this.cvs.getImageData(x, y, 1, 1)
    let arr = obj.data.toString().split(",")

    let first = parseInt(arr[0]).toString(16)
    first = first.length === 2 ? first : first + first

    let second = parseInt(arr[1]).toString(16)
    second = second.length === 2 ? second : second + second

    let third = parseInt(arr[2]).toString(16)
    third = third.length === 2 ? third : third + third

    let last = parseInt(arr.pop()) / 255
    last = last.toFixed(0)

    let color = {}
    color["rgba"] = "rgba(" + arr.join(",") + "," + last + ")"
    color["#"] = "#" + first + second + third
    return color
}
getImgColor.prototype.getColors = function() {

    /**
     * 避免图片过大，阻塞卡死
     * 每加载一行像素，延迟20毫秒加载下一行
     * return Promise 
     * promise resolve 解析完成后，返回颜色的总计数组，降序排列
     * promise reject none
     */

    return (new Promise((resolve, reject) => {

        let arr = []
        let getY = (i) => {
            for(let j = 0; j < this.canvas.height; j++) {
                let obj = {}
                obj = this.getColorXY(i, j)
                obj.index = 1
                let is = true

                arr.forEach((item) => {
                    if (item["#"] === obj["#"]) {
                        is = false
                        item.index += 1
                    }

                    let l = []

                    for (let i = 0; i < obj["#"].length; i++) {

                        if (item["#"].indexOf(obj["#"][i]) > -1) {
                            l.push("1")
                        }
                    }

                    let acc = (this.accuracy > 7) ? 7 : this.accuracy
                    acc = (this.accuracy < 1) ? 2 : this.accuracy
                    if (l.length > acc) {
                        is = false
                        item.index += 1
                    }
                })

                if (is) {
                    arr.push(obj)
                }
            }
        };

        let getX = (i) => {
            if (i < this.canvas.width) {

                getY(i)
                this.progress = (i / this.canvas.width * 100).toFixed(2) + "%"
                console.log(this.progress)
                setTimeout(() => {
                    getX(++i)
                }, 20)

            } else {

                this.progress = "100%"
                console.log( this.progress )

                resolve(arr.sort(function(a, b) {
                    return a.index < b.index ? 1 : (a.index > b.index ? -1 : 0)
                }))
            }
        };

        getX(0)

    }))
}

css

ul,li{
    list-style: none;
    margin: 0;
    padding: 0;
}
ul{
    margin: 20px auto;
    font-size: 0px;
}
ul li{
    display: inline-block;
    min-width: 100px;
    height: 50px;
    padding: 0 20px;
    margin: 1px;
    text-align: center;
    font-size: 15px;
    line-height: 50px;
    color: #000;
    border-radius: 4px;
    transition: all 0.3s linear 0s;
    cursor: pointer;
    border: 1px solid #e8e8e8;
}

ul li:hover{
    opacity: 0.8;
}