277 lines
8.0 KiB
JavaScript
277 lines
8.0 KiB
JavaScript
/**
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* covert canvas to image
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* and save the image file
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*/
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var Canvas2Image = function () {
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// check if support sth.
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var $support = function () {
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var canvas = document.createElement('canvas'),
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ctx = canvas.getContext('2d');
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return {
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canvas: !!ctx,
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imageData: !!ctx.getImageData,
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dataURL: !!canvas.toDataURL,
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btoa: !!window.btoa
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};
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}();
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var downloadMime = 'image/octet-stream';
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function scaleCanvas (canvas, width, height) {
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var w = canvas.width,
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h = canvas.height;
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if (width == undefined) {
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width = w;
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}
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if (height == undefined) {
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height = h;
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}
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var retCanvas = document.createElement('canvas');
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var retCtx = retCanvas.getContext('2d');
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retCanvas.width = width;
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retCanvas.height = height;
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retCtx.drawImage(canvas, 0, 0, w, h, 0, 0, width, height);
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return retCanvas;
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}
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function getDataURL (canvas, type, width, height) {
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canvas = scaleCanvas(canvas, width, height);
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return canvas.toDataURL(type);
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}
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function saveFile (strData,filename) {
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var save_link = document.createElement('a');
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save_link.href = strData;
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save_link.download = filename;
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var event = new MouseEvent('click',{"bubbles":false, "cancelable":false});
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save_link.dispatchEvent(event);
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}
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function genImage(strData) {
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var img = document.createElement('img');
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img.src = strData;
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return img;
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}
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function fixType (type) {
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type = type.toLowerCase().replace(/jpg/i, 'jpeg');
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var r = type.match(/png|jpeg|bmp|gif/)[0];
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return 'image/' + r;
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}
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function encodeData (data) {
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if (!window.btoa) { throw 'btoa undefined' }
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var str = '';
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if (typeof data == 'string') {
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str = data;
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} else {
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for (var i = 0; i < data.length; i ++) {
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str += String.fromCharCode(data[i]);
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}
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}
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return btoa(str);
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}
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function getImageData (canvas) {
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var w = canvas.width,
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h = canvas.height;
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return canvas.getContext('2d').getImageData(0, 0, w, h);
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}
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function makeURI (strData, type) {
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return 'data:' + type + ';base64,' + strData;
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}
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/**
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* create bitmap image
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* 按照规则生成图片响应头和响应体
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*/
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var genBitmapImage = function (oData) {
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//
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// BITMAPFILEHEADER: http://msdn.microsoft.com/en-us/library/windows/desktop/dd183374(v=vs.85).aspx
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// BITMAPINFOHEADER: http://msdn.microsoft.com/en-us/library/dd183376.aspx
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//
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var biWidth = oData.width;
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var biHeight = oData.height;
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var biSizeImage = biWidth * biHeight * 3;
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var bfSize = biSizeImage + 54; // total header size = 54 bytes
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//
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// typedef struct tagBITMAPFILEHEADER {
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// WORD bfType;
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// DWORD bfSize;
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// WORD bfReserved1;
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// WORD bfReserved2;
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// DWORD bfOffBits;
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// } BITMAPFILEHEADER;
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//
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var BITMAPFILEHEADER = [
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// WORD bfType -- The file type signature; must be "BM"
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0x42, 0x4D,
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// DWORD bfSize -- The size, in bytes, of the bitmap file
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bfSize & 0xff, bfSize >> 8 & 0xff, bfSize >> 16 & 0xff, bfSize >> 24 & 0xff,
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// WORD bfReserved1 -- Reserved; must be zero
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0, 0,
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// WORD bfReserved2 -- Reserved; must be zero
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0, 0,
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// DWORD bfOffBits -- The offset, in bytes, from the beginning of the BITMAPFILEHEADER structure to the bitmap bits.
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54, 0, 0, 0
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];
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//
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// typedef struct tagBITMAPINFOHEADER {
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// DWORD biSize;
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// LONG biWidth;
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// LONG biHeight;
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// WORD biPlanes;
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// WORD biBitCount;
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// DWORD biCompression;
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// DWORD biSizeImage;
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// LONG biXPelsPerMeter;
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// LONG biYPelsPerMeter;
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// DWORD biClrUsed;
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// DWORD biClrImportant;
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// } BITMAPINFOHEADER, *PBITMAPINFOHEADER;
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//
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var BITMAPINFOHEADER = [
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// DWORD biSize -- The number of bytes required by the structure
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40, 0, 0, 0,
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// LONG biWidth -- The width of the bitmap, in pixels
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biWidth & 0xff, biWidth >> 8 & 0xff, biWidth >> 16 & 0xff, biWidth >> 24 & 0xff,
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// LONG biHeight -- The height of the bitmap, in pixels
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biHeight & 0xff, biHeight >> 8 & 0xff, biHeight >> 16 & 0xff, biHeight >> 24 & 0xff,
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// WORD biPlanes -- The number of planes for the target device. This value must be set to 1
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1, 0,
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// WORD biBitCount -- The number of bits-per-pixel, 24 bits-per-pixel -- the bitmap
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// has a maximum of 2^24 colors (16777216, Truecolor)
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24, 0,
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// DWORD biCompression -- The type of compression, BI_RGB (code 0) -- uncompressed
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0, 0, 0, 0,
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// DWORD biSizeImage -- The size, in bytes, of the image. This may be set to zero for BI_RGB bitmaps
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biSizeImage & 0xff, biSizeImage >> 8 & 0xff, biSizeImage >> 16 & 0xff, biSizeImage >> 24 & 0xff,
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// LONG biXPelsPerMeter, unused
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0,0,0,0,
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// LONG biYPelsPerMeter, unused
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0,0,0,0,
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// DWORD biClrUsed, the number of color indexes of palette, unused
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0,0,0,0,
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// DWORD biClrImportant, unused
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0,0,0,0
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];
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var iPadding = (4 - ((biWidth * 3) % 4)) % 4;
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var aImgData = oData.data;
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var strPixelData = '';
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var biWidth4 = biWidth<<2;
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var y = biHeight;
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var fromCharCode = String.fromCharCode;
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do {
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var iOffsetY = biWidth4*(y-1);
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var strPixelRow = '';
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for (var x = 0; x < biWidth; x++) {
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var iOffsetX = x<<2;
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strPixelRow += fromCharCode(aImgData[iOffsetY+iOffsetX+2]) +
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fromCharCode(aImgData[iOffsetY+iOffsetX+1]) +
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fromCharCode(aImgData[iOffsetY+iOffsetX]);
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}
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for (var c = 0; c < iPadding; c++) {
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strPixelRow += String.fromCharCode(0);
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}
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strPixelData += strPixelRow;
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} while (--y);
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var strEncoded = encodeData(BITMAPFILEHEADER.concat(BITMAPINFOHEADER)) + encodeData(strPixelData);
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return strEncoded;
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};
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/**
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* [saveAsImage]
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* @param {[obj]} canvas [canvasElement]
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* @param {[Number]} width [optional] png width
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* @param {[Number]} height [optional] png height
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* @param {[String]} type [image type]
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* @param {[String]} filename [image filename]
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* @return {[type]} [description]
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*/
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var saveAsImage = function (canvas, width, height, type,filename) {
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if ($support.canvas && $support.dataURL) {
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if (typeof canvas == "string") { canvas = document.getElementById(canvas); }
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if (type == undefined) { type = 'png'; }
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filename = filename == undefined||filename.length === 0 ?Date.now()+'.'+type: filename+'.'+type
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type = fixType(type);
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if (/bmp/.test(type)) {
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var data = getImageData(scaleCanvas(canvas, width, height));
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var strData = genBitmapImage(data);
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saveFile(makeURI(strData, downloadMimedownloadMime),filename);
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} else {
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var strData = getDataURL(canvas, type, width, height);
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saveFile(strData.replace(type, downloadMime),filename);
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}
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}
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};
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var convertToImage = function (canvas, width, height, type) {
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if ($support.canvas && $support.dataURL) {
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if (typeof canvas == "string") { canvas = document.getElementById(canvas); }
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if (type == undefined) { type = 'png'; }
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type = fixType(type);
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if (/bmp/.test(type)) {
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var data = getImageData(scaleCanvas(canvas, width, height));
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var strData = genBitmapImage(data);
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return genImage(makeURI(strData, 'image/bmp'));
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} else {
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var strData = getDataURL(canvas, type, width, height);
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return genImage(strData);
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}
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}
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};
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return {
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saveAsImage: saveAsImage,
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saveAsPNG: function (canvas, width, height, fileName) {
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return saveAsImage(canvas, width, height, 'png',fileName);
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},
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saveAsJPEG: function (canvas, width, height, fileName) {
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return saveAsImage(canvas, width, height, 'jpeg',fileName);
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},
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saveAsGIF: function (canvas, width, height, fileName) {
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return saveAsImage(canvas, width, height, 'gif',fileName);
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},
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saveAsBMP: function (canvas, width, height, fileName) {
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return saveAsImage(canvas, width, height, 'bmp',fileName);
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},
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convertToImage: convertToImage,
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convertToPNG: function (canvas, width, height) {
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return convertToImage(canvas, width, height, 'png');
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},
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convertToJPEG: function (canvas, width, height) {
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return convertToImage(canvas, width, height, 'jpeg');
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},
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convertToGIF: function (canvas, width, height) {
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return convertToImage(canvas, width, height, 'gif');
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},
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convertToBMP: function (canvas, width, height) {
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return convertToImage(canvas, width, height, 'bmp');
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}
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};
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}();
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export default Canvas2Image |