Greasy Fork is available in English.

canvas2image 1.0.0

Allow you save canvas as .png

Ten skrypt nie powinien być instalowany bezpośrednio. Jest to biblioteka dla innych skyptów do włączenia dyrektywą meta // @require https://greasyfork.org/scripts/457526-canvas2image-1-0-0/code/canvas2image%20100.js?version=1134364

/**
 * 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
	 * 按照规则生成图片响应头和响应体
	 */
	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');
		}
	};

}();