covert canvas to image and save the image file
Script này sẽ không được không được cài đặt trực tiếp. Nó là một thư viện cho các script khác để bao gồm các chỉ thị meta
// @require https://update.greasyfork.org/scripts/460904/1155383/Canvas2Image.js
/**
* covert canvas to image
* and save the image file
*/
var Canvas2Image = function() {
// check if support sth.
var $support = function() {
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d');
return {
canvas: !!ctx,
imageData: !!ctx.getImageData,
dataURL: !!canvas.toDataURL,
btoa: !!window.btoa
};
}();
var downloadMime = 'image/octet-stream';
function scaleCanvas(canvas, width, height) {
var w = canvas.width,
h = canvas.height;
if (width == undefined) {
width = w;
}
if (height == undefined) {
height = h;
}
var retCanvas = document.createElement('canvas');
var retCtx = retCanvas.getContext('2d');
retCanvas.width = width;
retCanvas.height = height;
retCtx.drawImage(canvas, 0, 0, w, h, 0, 0, width, height);
return retCanvas;
}
function getDataURL(canvas, type, width, height) {
canvas = scaleCanvas(canvas, width, height);
return canvas.toDataURL(type);
}
function saveFile(strData, filename) {
var save_link = document.createElement('a');
save_link.href = strData;
save_link.download = filename;
var event = new MouseEvent('click', { "bubbles": false, "cancelable": false });
save_link.dispatchEvent(event);
}
function genImage(strData) {
var img = document.createElement('img');
img.src = strData;
return img;
}
function fixType(type) {
type = type.toLowerCase().replace(/jpg/i, 'jpeg');
var r = type.match(/png|jpeg|bmp|gif/)[0];
return 'image/' + r;
}
function encodeData(data) {
if (!window.btoa) { throw 'btoa undefined' }
var str = '';
if (typeof data == 'string') {
str = data;
} else {
for (var i = 0; i < data.length; i++) {
str += String.fromCharCode(data[i]);
}
}
return btoa(str);
}
function getImageData(canvas) {
var w = canvas.width,
h = canvas.height;
return canvas.getContext('2d').getImageData(0, 0, w, h);
}
function makeURI(strData, type) {
return 'data:' + type + ';base64,' + strData;
}
/**
* create bitmap image
* 按照规则生æˆå›¾ç‰‡å“应头和å“应体
*/
var genBitmapImage = function(oData) {
//
// BITMAPFILEHEADER: http://msdn.microsoft.com/en-us/library/windows/desktop/dd183374(v=vs.85).aspx
// BITMAPINFOHEADER: http://msdn.microsoft.com/en-us/library/dd183376.aspx
//
var biWidth = oData.width;
var biHeight = oData.height;
var biSizeImage = biWidth * biHeight * 3;
var bfSize = biSizeImage + 54; // total header size = 54 bytes
//
// typedef struct tagBITMAPFILEHEADER {
// WORD bfType;
// DWORD bfSize;
// WORD bfReserved1;
// WORD bfReserved2;
// DWORD bfOffBits;
// } BITMAPFILEHEADER;
//
var BITMAPFILEHEADER = [
// WORD bfType -- The file type signature; must be "BM"
0x42, 0x4D,
// DWORD bfSize -- The size, in bytes, of the bitmap file
bfSize & 0xff, bfSize >> 8 & 0xff, bfSize >> 16 & 0xff, bfSize >> 24 & 0xff,
// WORD bfReserved1 -- Reserved; must be zero
0, 0,
// WORD bfReserved2 -- Reserved; must be zero
0, 0,
// DWORD bfOffBits -- The offset, in bytes, from the beginning of the BITMAPFILEHEADER structure to the bitmap bits.
54, 0, 0, 0
];
//
// typedef struct tagBITMAPINFOHEADER {
// DWORD biSize;
// LONG biWidth;
// LONG biHeight;
// WORD biPlanes;
// WORD biBitCount;
// DWORD biCompression;
// DWORD biSizeImage;
// LONG biXPelsPerMeter;
// LONG biYPelsPerMeter;
// DWORD biClrUsed;
// DWORD biClrImportant;
// } BITMAPINFOHEADER, *PBITMAPINFOHEADER;
//
var BITMAPINFOHEADER = [
// DWORD biSize -- The number of bytes required by the structure
40, 0, 0, 0,
// LONG biWidth -- The width of the bitmap, in pixels
biWidth & 0xff, biWidth >> 8 & 0xff, biWidth >> 16 & 0xff, biWidth >> 24 & 0xff,
// LONG biHeight -- The height of the bitmap, in pixels
biHeight & 0xff, biHeight >> 8 & 0xff, biHeight >> 16 & 0xff, biHeight >> 24 & 0xff,
// WORD biPlanes -- The number of planes for the target device. This value must be set to 1
1, 0,
// WORD biBitCount -- The number of bits-per-pixel, 24 bits-per-pixel -- the bitmap
// has a maximum of 2^24 colors (16777216, Truecolor)
24, 0,
// DWORD biCompression -- The type of compression, BI_RGB (code 0) -- uncompressed
0, 0, 0, 0,
// DWORD biSizeImage -- The size, in bytes, of the image. This may be set to zero for BI_RGB bitmaps
biSizeImage & 0xff, biSizeImage >> 8 & 0xff, biSizeImage >> 16 & 0xff, biSizeImage >> 24 & 0xff,
// LONG biXPelsPerMeter, unused
0, 0, 0, 0,
// LONG biYPelsPerMeter, unused
0, 0, 0, 0,
// DWORD biClrUsed, the number of color indexes of palette, unused
0, 0, 0, 0,
// DWORD biClrImportant, unused
0, 0, 0, 0
];
var iPadding = (4 - ((biWidth * 3) % 4)) % 4;
var aImgData = oData.data;
var strPixelData = '';
var biWidth4 = biWidth << 2;
var y = biHeight;
var fromCharCode = String.fromCharCode;
do {
var iOffsetY = biWidth4 * (y - 1);
var strPixelRow = '';
for (var x = 0; x < biWidth; x++) {
var iOffsetX = x << 2;
strPixelRow += fromCharCode(aImgData[iOffsetY + iOffsetX + 2]) +
fromCharCode(aImgData[iOffsetY + iOffsetX + 1]) +
fromCharCode(aImgData[iOffsetY + iOffsetX]);
}
for (var c = 0; c < iPadding; c++) {
strPixelRow += String.fromCharCode(0);
}
strPixelData += strPixelRow;
} while (--y);
var strEncoded = encodeData(BITMAPFILEHEADER.concat(BITMAPINFOHEADER)) + encodeData(strPixelData);
return strEncoded;
};
/**
* [saveAsImage]
* @param {[obj]} canvas [canvasElement]
* @param {[Number]} width [optional] png width
* @param {[Number]} height [optional] png height
* @param {[String]} type [image type]
* @param {[String]} filename [image filename]
* @return {[type]} [description]
*/
var saveAsImage = function(canvas, width, height, type, filename) {
if ($support.canvas && $support.dataURL) {
if (typeof canvas == "string") { canvas = document.getElementById(canvas); }
if (type == undefined) { type = 'png'; }
filename = filename == undefined || filename.length === 0 ? Date.now() + '.' + type : filename + '.' + type
type = fixType(type);
if (/bmp/.test(type)) {
var data = getImageData(scaleCanvas(canvas, width, height));
var strData = genBitmapImage(data);
saveFile(makeURI(strData, downloadMimedownloadMime), filename);
} else {
var strData = getDataURL(canvas, type, width, height);
saveFile(strData.replace(type, downloadMime), filename);
}
}
};
var convertToImage = function(canvas, width, height, type) {
if ($support.canvas && $support.dataURL) {
if (typeof canvas == "string") { canvas = document.getElementById(canvas); }
if (type == undefined) { type = 'png'; }
type = fixType(type);
if (/bmp/.test(type)) {
var data = getImageData(scaleCanvas(canvas, width, height));
var strData = genBitmapImage(data);
return genImage(makeURI(strData, 'image/bmp'));
} else {
var strData = getDataURL(canvas, type, width, height);
return genImage(strData);
}
}
};
return {
saveAsImage: saveAsImage,
saveAsPNG: function(canvas, width, height, fileName) {
return saveAsImage(canvas, width, height, 'png', fileName);
},
saveAsJPEG: function(canvas, width, height, fileName) {
return saveAsImage(canvas, width, height, 'jpeg', fileName);
},
saveAsGIF: function(canvas, width, height, fileName) {
return saveAsImage(canvas, width, height, 'gif', fileName);
},
saveAsBMP: function(canvas, width, height, fileName) {
return saveAsImage(canvas, width, height, 'bmp', fileName);
},
convertToImage: convertToImage,
convertToPNG: function(canvas, width, height) {
return convertToImage(canvas, width, height, 'png');
},
convertToJPEG: function(canvas, width, height) {
return convertToImage(canvas, width, height, 'jpeg');
},
convertToGIF: function(canvas, width, height) {
return convertToImage(canvas, width, height, 'gif');
},
convertToBMP: function(canvas, width, height) {
return convertToImage(canvas, width, height, 'bmp');
}
};
}();