从base64 PNG获取高度和宽度尺寸
我有这个
data:image/png;base64,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 我想使用JavaScript从这个字符串中获取高度和宽度。 我该怎么办？ 它甚至可能吗？
您可以假设访问jQuery，window.btoa和window.atob。
我确信有可能以某种方式解析PNG，但假设数据URI支持（因为我们可以假设atob ），你可以创建一个图像并等待它加载（这适用于任何格式）：
var image = document.createElement('img'); image.addEventListener('load', function() { // image.width × image.height }); image.src = 'data:image/png;base64,…';
这是一个演示。
好的，显然你想手动提取这些信息。 PNG文件以字节89 50 4E 47 0D 01 1A 0A开头，后跟包含宽度和高度的IHDR块，必须是第一个块。 （是的，更容易！）块有4字节长度，4字节类型，然后是长度字节内容。 IHDR的内容以4字节宽度和4字节高度开头，因此PNG的宽度和高度始终为16-24字节！ 如果您愿意，可以全部检查，但是假设PNG有效的简单方法：
function toInt32(bytes) { return (bytes[0] << 24) | (bytes[1] << 16) | (bytes[2] << 8) | bytes[3]; } function getDimensions(data) { return { width: toInt32(data.slice(16, 20)), height: toInt32(data.slice(20, 24)) }; } var base64Characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'; function base64Decode(data) { var result = []; var current = 0; for(var i = 0, c; c = data.charAt(i); i++) { if(c === '=') { if(i !== data.length - 1 && (i !== data.length - 2 || data.charAt(i + 1) !== '=')) { throw new SyntaxError('Unexpected padding character.'); } break; } var index = base64Characters.indexOf(c); if(index === -1) { throw new SyntaxError('Invalid Base64 character.'); } current = (current << 6) | index; if(i % 4 === 3) { result.push(current >> 16, (current & 0xff00) >> 8, current & 0xff); current = 0; } } if(i % 4 === 1) { throw new SyntaxError('Invalid length for a Base64 string.'); } if(i % 4 === 2) { result.push(current >> 4); } else if(i % 4 === 3) { current <<= 6; result.push(current >> 16, (current & 0xff00) >> 8); } return result; }
这是一个演示。
现场演示
var imgData = 'data:image/png;base64,iVBORw0.........'; var img = new Image(); img.onload = function(){ alert(img.width +' '+ img.height ); }; img.src = imgData;
这是3年后新的更新的es6版本，带有一些同步的类型数组的帮助，你不需要将孔图像加载到内存中来解决它。 所以它更快:)
也不需要任何DOM，因此它可以在Workers内部工作
function getPngDimensions(base64) { const header = atob(base64.slice(0, 50)).slice(16,24) const uint8 = Uint8Array.from(header, c => c.charCodeAt(0)) const dataView = new DataView(uint8.buffer) return { width: dataView.getInt32(0), height: dataView.getInt32(4) } } // Just to get some base64 png example var canvas = document.createElement('canvas') var base64 = canvas.toDataURL().split(',')[1] var dimensions = getPngDimensions(base64) console.log(dimensions)
使用jQuery：
var width, height; $('![]()
').load(function(){ width = $(this).width(); height = $(this).height(); // Call whatever function here that requires the width/height }).attr('src', datauri)
**在node.js中
function getPNGSize (buffer) { if (buffer.toString('ascii', 12, 16) === 'CgBI') { return { 'width': buffer.readUInt32BE(32), 'height': buffer.readUInt32BE(36) }; } return { 'width': buffer.readUInt32BE(16), 'height': buffer.readUInt32BE(20) }; } getPNGSize(buffer)