使用JavaScript canvas實作圖片裁切_jquery

canvas是一個可以讓我們使用腳本繪圖的標籤，它提供了一系列完整的屬性和方法。我們可以藉此來實現圖形繪製，圖像處理甚至實現簡單的動畫和遊戲製作。

canvas標籤只有兩個屬性：width和height，用來設定畫布的寬和高，如果沒有透過標籤屬性或腳本來設置，預設為300*150;

好了，canvas的介紹就先到這裡，下面我們來看看javascript結合canvas實作圖片的裁切程式碼：

複製程式碼 程式碼如下:

var selectObj = null;
function ImageCrop(canvasId, imageSource, x, y, width, height) {
    var canvas = $("#" canvasId);
    if (canvas.length == 0 && imageSource) {
        返回；
    }
    函數canvasMouseDown(e) {
        停止選擇(e);
        canvas.css("遊標", "預設");
    }
    函數canvasMouseMove(e) {
        var canvasOffset = canvas.offset();
        var pageX = e.pageX || event.targetTouches[0].pageX;
        var pageY = e.pageY || event.targetTouches[0].pageY;
        iMouseX = Math.floor(pageX - canvasOffset.left);
        iMouseY = Math.floor(pageY - canvasOffset.top);
        canvas.css("遊標", "預設");
        if (selectObj.bDragAll) {
            canvas.css("遊標", "移動");
            canvas.data("拖曳", true);
            var cx = iMouseX - selectObj.px;
            CX = CX             mx = ctx.canvas.width - selectObj.w;
            cx=cx> MX？ mx : cx;
            selectObj.x = cx;
            var cy = iMouseY - selectObj.py;
            cy＝cy＜ 0 ? 0 : cy;
            my = ctx.canvas.height - selectObj.h;
            cy＝cy＞我的 ？我的：cy；
            selectObj.y = cy;
        }
        for (var i = 0; i             selectObj.bHow[i] = false;
            selectObj.iCSize[i] = selectObj.csize;
        }
        // 將滑鼠停留在調整大小的立方體上
        if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX             iMouseY> selectObj.y - selectObj.csizeh && iMouseY             canvas.css("遊標", "指標");
            selectObj.bHow[0] = true;
            selectObj.iCSize[0] = selectObj.csizeh;
        }
        if (iMouseX > selectObj.x selectObj.w - selectObj.csizeh && iMouseX             iMouseY> selectObj.y - selectObj.csizeh && iMouseY             canvas.css("遊標", "指標");
            selectObj.bHow[1] = true;
            selectObj.iCSize[1] = selectObj.csizeh;
        }
        if (iMouseX > selectObj.x selectObj.w - selectObj.csizeh && iMouseX             iMouseY> selectObj.y selectObj.h - selectObj.csizeh && iMouseY             selectObj.bHow[2] = true;
            selectObj.iCSize[2] = selectObj.csizeh;
        }
        if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX             iMouseY> selectObj.y selectObj.h - selectObj.csizeh && iMouseY             canvas.css("螢幕", "指標");
            selectObj.bHow[3] = true;
            selectObj.iCSize[3] = selectObj.csizeh;
        }
        if (iMouseX > selectObj.x && iMouseX selectObj.y && iMouseY             canvas.css("左上角", "移動");
        }
        //如果拖曳調整立方體大小
        var iFW、iFH、iFX、iFY、mx、我的；
        if (selectObj.bDrag[0]) {
            iFX = iMouseX - selectObj.px;
            iFY = iMouseY - selectObj.py;
            iFW = selectObj.w selectObj.x - iFX;
            iFH = selectObj.h selectObj.y - iFY;
            canvas.data("拖曳", true);
        }
        if (selectObj.bDrag[1]) {
            iFX = selectObj.x;
            iFY = iMouseY - selectObj.py;
            iFW = iMouseX - selectObj.px - iFX;
            iFH = selectObj.h selectObj.y - iFY;
            canvas.data("拖曳", true);
        }
        if (selectObj.bDrag[2]) {
            iFX = selectObj.x;
            iFY = selectObj.y;
            iFW = iMouseX - selectObj.px - iFX;
            iFH = iMouseY - selectObj.py - iFY;
            canvas.data("拖曳", true);
        }
        if (selectObj.bDrag[3]) {
            iFX = iMouseX - selectObj.px;
            iFY = selectObj.y;
            iFW = selectObj.w selectObj.x - iFX;
            iFH = iMouseY - selectObj.py - iFY;
            canvas.data("拖曳", true);
        }
        if (iFW > selectObj.csizeh * 2 && iFH > selectObj.csizeh * 2) {
            selectObj.w = iFW;
            selectObj.h = iFH;
            selectObj.x = iFX;
            selectObj.y = iFY;
        }
        相關場景();
    }
    函數canvasMouseOut() {
        $(canvas).trigger("mouseup");
    }
    函數canvasMouseUp() {
        selectObj.bDragAll = false;
        for (var i = 0; i             selectObj.bDrag[i] = false;
        }
        canvas.css("遊標", "預設");
        canvas.data("選擇", {
            x: selectObj.x,
            y: selectObj.y,
            w: selectObj.w,
            h: selectObj.h
        });
        selectObj.px = 0;
        selectObj.py = 0;
    }
    函數選擇(x, y, w, h) {
        這個.x = x; // 初始位置
        this.y = y;
        這個.w = w; // 和大小
        this.h = h;
        這個.px = x; // 用來拖曳計算的額外變數
        this.py = y;
        這個.csize = 4; // 調整立方體大小
        this.csizeh = 6; // 調整立方體大小（懸停時）
        this.bHow = [假，假，假，假]; // 懸停狀態
        this.iCSize = [this.csize, this.csize, this.csize, this.csize]; // 調整立方體大小
        this.bDrag = [假，假，假，假]; // 拖曳狀態
        this.bDragAll = false; // 拖曳整個選擇
    }
    Selection.prototype.draw = function () {
        ctx.StrongStyle = '#666';
        ctx.lineWidth = 2;
        ctx.lines(this.x, this.y, this.w, this.h);
        // 繪製原始影像的一部份
        if (this.w > 0 && this.h > 0) {
            ctx.drawImage(映像, this.x, this.y, this.w, this.h, this.x, this.y, this.w, this.h);
        }
        // 繪製調整大小的立方體
        ctx.fillStyle = '#999';
        ctx.fillRect(this.x - this.iCSize[0], this.y - this.iCSize[0], this.iCSize[0] * 2, this.iCSize[0] * 2);
ctx.fillRect(this.x this.w - this.iCSize[1], this.y - this.iCSize[1], this.iCSize[1] * 2, this.iCSize[1] * 2);
ctx.fillRect(this.x this.w - this.iCSize[2], this.y this.h - this.iCSize[2], this.iCSize[2] * 2, this.iCSize[2] * 2) ;
ctx.fillRect(this.x - this.iCSize[3], this.y this.h - this.iCSize[3], this.iCSize[3] * 2, this.iCSize[3] * 2);
    };
    var drawScene = function () {
        ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // 清除畫布
        // 繪製來源影像
        ctx.drawImage(image, 0, 0, ctx.canvas.width, ctx.canvas.height);
        // 並使其變暗
        ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
        ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
        // 繪製選區
        selectObj.draw();
        canvas.mousedown(canvasMouseDown);
        canvas.on("touchstart", canvasMouseDown);
    };
    var createSelection = function (x, y, width, height) {
        var content = $("#imagePreview");
        x = x || Math.ceil((content.width() - 寬度) / 2);
        y = y || Math.ceil((content.height() - 高度) / 2);
        回新的選擇（x，y，寬度，高度）；
    };
    var ctx = canvas[0].getContext("2d");
    var iMouseX = 1;
    var iMouseY = 1;
    var image = new Image();
    image.onload = function () {
        selectObj = createSelection(x, y, 寬度, 高度);
        canvas.data("選擇", {
            x: selectObj.x,
            y: selectObj.y,
            w: selectObj.w,
            h: selectObj.h
        });
        繪製場景();
    };
    image.src = imageSource;
    canvas.mousemove(canvasMouseMove);
    canvas.on("touchmove", canvasMouseMove);
    var StopSelect = function (e) {
        var canvasOffset = $(canvas).offset();
        var pageX = e.pageX || event.targetTouches[0].pageX;
        var pageY = e.pageY || event.targetTouches[0].pageY;
        iMouseX = Math.floor(pageX - canvasOffset.left);
        iMouseY = Math.floor(pageY - canvasOffset.top);
        selectObj.px = iMouseX - selectObj.x;
        selectObj.py = iMouseY - selectObj.y;
        if (selectObj.bHow[0]) {
            selectObj.px = iMouseX - selectObj.x;
            selectObj.py = iMouseY - selectObj.y;
        }
        if (selectObj.bHow[1]) {
            selectObj.px = iMouseX - selectObj.x - selectObj.w;
            selectObj.py = iMouseY - selectObj.y;
        }
        if (selectObj.bHow[2]) {
            selectObj.px = iMouseX - selectObj.x - selectObj.w;
            selectObj.py = iMouseY - selectObj.y - selectObj.h;
        }
        if (selectObj.bHow[3]) {
            selectObj.px = iMouseX - selectObj.x;
            selectObj.py = iMouseY - selectObj.y - selectObj.h;
        }
        if (iMouseX > selectObj.x selectObj.csizeh &&
            iMouseX             iMouseY> selectObj.y selectObj.csizeh &&
            iMouseY             selectObj.bDragAll = true;
        }
        for (var i = 0; i             if (selectObj.bHow[i]) {
                selectObj.bDrag[i] = true;
            }
        }
    };
    canvas.mouseout(canvasMouseOut);
    canvas.mouseup(canvasMouseUp);
    canvas.on("touchend", canvasMouseUp);
    this.getImageData = function (previewID) {
        var tmpCanvas = $("")[0];
        var tmpCtx = tmpCanvas.getContext("2d");
        if (tmpCanvas && selectObj) {
            tmpCanvas.width = selectObj.w;
            tmpCanvas.height = selectObj.h;
            tmpCtx.drawImage(image, selectObj.x, selectObj.y, selectObj.w, selectObj.h, 0, 0, selectObj.w, selectObj.h);
            if (document.getElementById(previewID)) {
                document.getElementById(previewID).src = tmpCanvas.toDataURL();
                document.getElementById(previewID).style.border = "1px 實心#ccc";
            }
            return tmpCanvas.toDataURL();
        }
    };
}
函數 autoResizeImage(maxWidth, maxHeight, objImg) {
    var img = new Image();
    img.src = objImg.src;
    var hRatio;
    var wRatio;
    無功分數 = 1;
    var w = objImg.width;
    var h = objImg.height;
    wRatio = maxWidth / w;
    hRatio = maxHeight / h;
    if (w         返回；
    }
    if (maxWidth == 0 && maxHeight == 0) {
        份數 = 1;
    } else if (maxWidth == 0) {
        if (hRatio             分別 = hRatio;
        }
    } else if (maxHeight == 0) {
        if (wRatio             比例 = wRatio;
        }
    } else if (wRatio         其中 = (wRatio     }其他{
        其中 = (wRatio     }
    if (共有         if (比率             各個 = 1 - 各個;
        }
        w = w * 各;
        h = h * 各;
    }
    objImg.height = h;
    objImg.width = w;
}

朋友們拿去試試吧，希望大家能夠喜歡，有疑問就給我留言吧。