【踩坑】為base64編碼的圖片生成截圖不顯示
阿新 • • 發佈:2019-01-08
問題
在effevo中設定個人頭像時,會有無法顯示的情況,還不穩定重現,終於抓到問題原因,下面分享下解決方法
解決方法
先看下原始寫法
var imgBase64='data:image/png;base64,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'
var img = window.document.createElement('img');
img.src = imgBase64;
//裁剪
console.log('img.width , img.height', img.width, img.height);
if (!img.width || !img.height) {
console.log('img', img);
throw { msg: '裁剪圖片失敗,請重新選擇圖片' };
}
if (img.width > img.height) {
var sx = (img.width - img.height) / 2;
var sy = 0;
var maxSize = img.height;
}
else {
var sx = 0;
var sy = (img.height - img.width) / 2;
var maxSize = img.width;
}
var canvas = document.createElement('canvas');
canvas.width = size;
canvas.height = size;
var context = canvas.getContext("2d");
context.drawImage(img, sx, sy, maxSize, maxSize, 0, 0, size, size);
var base64 = canvas.toDataURL('image/png');
var imgData = base64.split(',')[1];
var binaryData = window.atob(imgData);
var ia = new Uint8Array(binaryData.length);
for (var i = 0; i < binaryData.length; i++) {
ia[i] = binaryData.charCodeAt(i);
}
var blob = new Blob([ia], { type: "image/png" });
console.log('blob.size', blob.size);
return blob;
如上程式碼在99%的情況下都沒有問題,但偶爾:
console.log('img.width , img.height', img.width, img.height);
這句話會輸出:
img.width , img.height',0,0
注意,圖片高度、寬度為0!!!!!!
圖片是有高度和寬度的,但這種寫法卻沒有,導致圖片不顯示!!!
如下寫才是安全的:
img.onload=function(e){
console.log('img.width , img.height', img.width, img.height);
//開始截圖等程式碼
}
也就是說img.src=imgBase64後,不能保證img物件同步生成