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  • 用canvas裁剪图片

      1 var selectObj = null;
      2 function ImageCrop(canvasId, imageSource, x, y, width, height) {
      3     var canvas = $("#" + canvasId);
      4     if (canvas.length == 0 && imageSource) {
      5         return;
      6     }
      7 
      8     function canvasMouseDown(e) {
      9         StopSelect(e);
     10         canvas.css("cursor", "default");
     11     }
     12 
     13     function canvasMouseMove(e) {
     14         var canvasOffset = canvas.offset();
     15         var pageX = e.pageX || event.targetTouches[0].pageX;
     16         var pageY = e.pageY || event.targetTouches[0].pageY;
     17         iMouseX = Math.floor(pageX - canvasOffset.left);
     18         iMouseY = Math.floor(pageY - canvasOffset.top);
     19 
     20         canvas.css("cursor", "default");
     21         if (selectObj.bDragAll) {
     22             canvas.css("cursor", "move");
     23             canvas.data("drag", true);
     24             var cx = iMouseX - selectObj.px;
     25             cx = cx < 0 ? 0 : cx;
     26             mx = ctx.canvas.width - selectObj.w;
     27             cx = cx > mx ? mx : cx;
     28             selectObj.x = cx;
     29             var cy = iMouseY - selectObj.py;
     30             cy = cy < 0 ? 0 : cy;
     31             my = ctx.canvas.height - selectObj.h;
     32             cy = cy > my ? my : cy;
     33             selectObj.y = cy;
     34         }
     35         for (var i = 0; i < 4; i++) {
     36             selectObj.bHow[i] = false;
     37             selectObj.iCSize[i] = selectObj.csize;
     38         }
     39 
     40         // hovering over resize cubes
     41         if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX < selectObj.x + selectObj.csizeh &&
     42             iMouseY > selectObj.y - selectObj.csizeh && iMouseY < selectObj.y + selectObj.csizeh) {
     43             canvas.css("cursor", "pointer");
     44             selectObj.bHow[0] = true;
     45             selectObj.iCSize[0] = selectObj.csizeh;
     46         }
     47         if (iMouseX > selectObj.x + selectObj.w - selectObj.csizeh && iMouseX < selectObj.x + selectObj.w + selectObj.csizeh &&
     48             iMouseY > selectObj.y - selectObj.csizeh && iMouseY < selectObj.y + selectObj.csizeh) {
     49             canvas.css("cursor", "pointer");
     50 
     51             selectObj.bHow[1] = true;
     52             selectObj.iCSize[1] = selectObj.csizeh;
     53         }
     54         if (iMouseX > selectObj.x + selectObj.w - selectObj.csizeh && iMouseX < selectObj.x + selectObj.w + selectObj.csizeh &&
     55             iMouseY > selectObj.y + selectObj.h - selectObj.csizeh && iMouseY < selectObj.y + selectObj.h + selectObj.csizeh) {
     56             canvas.css("cursor", "pointer");
     57 
     58             selectObj.bHow[2] = true;
     59             selectObj.iCSize[2] = selectObj.csizeh;
     60         }
     61         if (iMouseX > selectObj.x - selectObj.csizeh && iMouseX < selectObj.x + selectObj.csizeh &&
     62             iMouseY > selectObj.y + selectObj.h - selectObj.csizeh && iMouseY < selectObj.y + selectObj.h + selectObj.csizeh) {
     63             canvas.css("cursor", "pointer");
     64 
     65             selectObj.bHow[3] = true;
     66             selectObj.iCSize[3] = selectObj.csizeh;
     67         }
     68 
     69         if (iMouseX > selectObj.x && iMouseX < selectObj.x + selectObj.w && iMouseY > selectObj.y && iMouseY < selectObj.y + selectObj.h) {
     70             canvas.css("cursor", "move");
     71         }
     72 
     73         // in case of dragging of resize cubes
     74         var iFW, iFH, iFX, iFY, mx, my;
     75         if (selectObj.bDrag[0]) {
     76             iFX = iMouseX - selectObj.px;
     77             iFY = iMouseY - selectObj.py;
     78             iFW = selectObj.w + selectObj.x - iFX;
     79             iFH = selectObj.h + selectObj.y - iFY;
     80             canvas.data("drag", true);
     81         }
     82         if (selectObj.bDrag[1]) {
     83             iFX = selectObj.x;
     84             iFY = iMouseY - selectObj.py;
     85             iFW = iMouseX - selectObj.px - iFX;
     86             iFH = selectObj.h + selectObj.y - iFY;
     87             canvas.data("drag", true);
     88         }
     89         if (selectObj.bDrag[2]) {
     90             iFX = selectObj.x;
     91             iFY = selectObj.y;
     92             iFW = iMouseX - selectObj.px - iFX;
     93             iFH = iMouseY - selectObj.py - iFY;
     94             canvas.data("drag", true);
     95         }
     96         if (selectObj.bDrag[3]) {
     97             iFX = iMouseX - selectObj.px;
     98             iFY = selectObj.y;
     99             iFW = selectObj.w + selectObj.x - iFX;
    100             iFH = iMouseY - selectObj.py - iFY;
    101             canvas.data("drag", true);
    102         }
    103 
    104         if (iFW > selectObj.csizeh * 2 && iFH > selectObj.csizeh * 2) {
    105             selectObj.w = iFW;
    106             selectObj.h = iFH;
    107             selectObj.x = iFX;
    108             selectObj.y = iFY;
    109         }
    110         drawScene();
    111     }
    112 
    113     function canvasMouseOut() {
    114         $(canvas).trigger("mouseup");
    115     }
    116 
    117     function canvasMouseUp() {
    118         selectObj.bDragAll = false;
    119         for (var i = 0; i < 4; i++) {
    120             selectObj.bDrag[i] = false;
    121         }
    122         canvas.css("cursor", "default");
    123         canvas.data("select", {
    124             x: selectObj.x,
    125             y: selectObj.y,
    126             w: selectObj.w,
    127             h: selectObj.h
    128         });
    129         selectObj.px = 0;
    130         selectObj.py = 0;
    131     }
    132 
    133     function Selection(x, y, w, h) {
    134         this.x = x; // initial positions
    135         this.y = y;
    136         this.w = w; // and size
    137         this.h = h;
    138 
    139         this.px = x; // extra variables to dragging calculations
    140         this.py = y;
    141 
    142         this.csize = 4; // resize cubes size
    143         this.csizeh = 6; // resize cubes size (on hover)
    144 
    145         this.bHow = [false, false, false, false]; // hover statuses
    146         this.iCSize = [this.csize, this.csize, this.csize, this.csize]; // resize cubes sizes
    147         this.bDrag = [false, false, false, false]; // drag statuses
    148         this.bDragAll = false; // drag whole selection
    149     }
    150 
    151     Selection.prototype.draw = function () {
    152         ctx.strokeStyle = '#666';
    153         ctx.lineWidth = 2;
    154         ctx.strokeRect(this.x, this.y, this.w, this.h);
    155 
    156         // draw part of original image
    157         if (this.w > 0 && this.h > 0) {
    158             ctx.drawImage(image, this.x, this.y, this.w, this.h, this.x, this.y, this.w, this.h);
    159         }
    160 
    161         // draw resize cubes
    162         ctx.fillStyle = '#999';
    163         ctx.fillRect(this.x - this.iCSize[0], this.y - this.iCSize[0], this.iCSize[0] * 2, this.iCSize[0] * 2);
    164         ctx.fillRect(this.x + this.w - this.iCSize[1], this.y - this.iCSize[1], this.iCSize[1] * 2, this.iCSize[1] * 2);
    165         ctx.fillRect(this.x + this.w - this.iCSize[2], this.y + this.h - this.iCSize[2], this.iCSize[2] * 2, this.iCSize[2] * 2);
    166         ctx.fillRect(this.x - this.iCSize[3], this.y + this.h - this.iCSize[3], this.iCSize[3] * 2, this.iCSize[3] * 2);
    167     };
    168 
    169     var drawScene = function () {
    170         ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // clear canvas
    171 
    172         // draw source image
    173         ctx.drawImage(image, 0, 0, ctx.canvas.width, ctx.canvas.height);
    174 
    175         // and make it darker
    176         ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
    177         ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height);
    178 
    179         // draw selection
    180         selectObj.draw();
    181         canvas.mousedown(canvasMouseDown);
    182         canvas.on("touchstart", canvasMouseDown);
    183     };
    184 
    185     var createSelection = function (x, y, width, height) {
    186         var content = $("#imagePreview");
    187         x = x || Math.ceil((content.width() - width) / 2);
    188         y = y || Math.ceil((content.height() - height) / 2);
    189         return new Selection(x, y, width, height);
    190     };
    191 
    192     var ctx = canvas[0].getContext("2d");
    193     var iMouseX = 1;
    194     var iMouseY = 1;
    195     var image = new Image();
    196     image.onload = function () {
    197         selectObj = createSelection(x, y, width, height);
    198         canvas.data("select", {
    199             x: selectObj.x,
    200             y: selectObj.y,
    201             w: selectObj.w,
    202             h: selectObj.h
    203         });
    204         drawScene();
    205     };
    206     image.src = imageSource;
    207 
    208     canvas.mousemove(canvasMouseMove);
    209     canvas.on("touchmove", canvasMouseMove);
    210 
    211     var StopSelect = function (e) {
    212         var canvasOffset = $(canvas).offset();
    213         var pageX = e.pageX || event.targetTouches[0].pageX;
    214         var pageY = e.pageY || event.targetTouches[0].pageY;
    215         iMouseX = Math.floor(pageX - canvasOffset.left);
    216         iMouseY = Math.floor(pageY - canvasOffset.top);
    217 
    218         selectObj.px = iMouseX - selectObj.x;
    219         selectObj.py = iMouseY - selectObj.y;
    220 
    221         if (selectObj.bHow[0]) {
    222             selectObj.px = iMouseX - selectObj.x;
    223             selectObj.py = iMouseY - selectObj.y;
    224         }
    225         if (selectObj.bHow[1]) {
    226             selectObj.px = iMouseX - selectObj.x - selectObj.w;
    227             selectObj.py = iMouseY - selectObj.y;
    228         }
    229         if (selectObj.bHow[2]) {
    230             selectObj.px = iMouseX - selectObj.x - selectObj.w;
    231             selectObj.py = iMouseY - selectObj.y - selectObj.h;
    232         }
    233         if (selectObj.bHow[3]) {
    234             selectObj.px = iMouseX - selectObj.x;
    235             selectObj.py = iMouseY - selectObj.y - selectObj.h;
    236         }
    237 
    238         if (iMouseX > selectObj.x + selectObj.csizeh &&
    239             iMouseX < selectObj.x + selectObj.w - selectObj.csizeh &&
    240             iMouseY > selectObj.y + selectObj.csizeh &&
    241             iMouseY < selectObj.y + selectObj.h - selectObj.csizeh) {
    242             selectObj.bDragAll = true;
    243         }
    244 
    245         for (var i = 0; i < 4; i++) {
    246             if (selectObj.bHow[i]) {
    247                 selectObj.bDrag[i] = true;
    248             }
    249         }
    250     };
    251     canvas.mouseout(canvasMouseOut);
    252     canvas.mouseup(canvasMouseUp);
    253     canvas.on("touchend", canvasMouseUp);
    254 
    255     this.getImageData = function (previewID) {
    256         var tmpCanvas = $("<canvas></canvas>")[0];
    257         var tmpCtx = tmpCanvas.getContext("2d");
    258         if (tmpCanvas && selectObj) {
    259             tmpCanvas.width = selectObj.w;
    260             tmpCanvas.height = selectObj.h;
    261             tmpCtx.drawImage(image, selectObj.x, selectObj.y, selectObj.w, selectObj.h, 0, 0, selectObj.w, selectObj.h);
    262             if (document.getElementById(previewID)) {
    263                 document.getElementById(previewID).src = tmpCanvas.toDataURL();
    264                 document.getElementById(previewID).style.border = "1px solid #ccc";
    265             }
    266             return tmpCanvas.toDataURL();
    267         }
    268     };
    269 }
    270 
    271 function autoResizeImage(maxWidth, maxHeight, objImg) {
    272     var img = new Image();
    273     img.src = objImg.src;
    274     var hRatio;
    275     var wRatio;
    276     var ratio = 1;
    277     var w = objImg.width;
    278     var h = objImg.height;
    279     wRatio = maxWidth / w;
    280     hRatio = maxHeight / h;
    281     if (w < maxWidth && h < maxHeight) {
    282         return;
    283     }
    284     if (maxWidth == 0 && maxHeight == 0) {
    285         ratio = 1;
    286     } else if (maxWidth == 0) {
    287         if (hRatio < 1) {
    288             ratio = hRatio;
    289         }
    290     } else if (maxHeight == 0) {
    291         if (wRatio < 1) {
    292             ratio = wRatio;
    293         }
    294     } else if (wRatio < 1 || hRatio < 1) {
    295         ratio = (wRatio <= hRatio ? wRatio : hRatio);
    296     } else {
    297         ratio = (wRatio <= hRatio ? wRatio : hRatio) - Math.floor(wRatio <= hRatio ? wRatio : hRatio);
    298     }
    299     if (ratio < 1) {
    300         if (ratio < 0.5 && w < maxWidth && h < maxHeight) {
    301             ratio = 1 - ratio;
    302         }
    303         w = w * ratio;
    304         h = h * ratio;
    305     }
    306     objImg.height = h;
    307     objImg.width = w;
    308 }
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  • 原文地址:https://www.cnblogs.com/jessiecaisme/p/4260436.html
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