Blob/DataURL/canvas/image的相互转换
// canvas转dataURL：canvas对象、转换格式、图像品质
function canvasToDataURL(canvas, format, quality){
return canvas.toDataURL(format||'image/jpeg', quality||1.0);
}
// DataURL转canvas
function dataURLToCanvas(dataurl, cb){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var img = new Image();
img.onload = function(){
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
cb(canvas);
};
img.src = dataurl;
}
/*-----------------------------------------------------------------------*/
// image转canvas：图片地址
function imageToCanvas(src, cb){
var canvas = document.createElement('CANVAS');
var ctx = canvas.getContext('2d');
var img = new Image();
img.src = src;
img.onload = function (){
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
cb(canvas);
};
}
// canvas转image
function canvasToImage(canvas){
var img = new Image();
img.src = canvas.toDataURL('image/jpeg', 1.0);
return img;
}
/*-----------------------------------------------------------------------*/
// File/Blob对象转DataURL
function fileOrBlobToDataURL(obj, cb){
var a = new FileReader();
a.readAsDataURL(obj);
a.onload = function (e){
cb(e.target.result);
};
}
// DataURL转Blob对象
function dataURLToBlob(dataurl){
var arr = dataurl.split(',');
var mime = arr[0].match(/:(.*?);/)[1];
var bstr = atob(arr[1]);
var n = bstr.length;
var u8arr = new Uint8Array(n);
while(n--){
u8arr[n] = bstr.charCodeAt(n);
}
return new Blob([u8arr], {type:mime});
}
/*-----------------------------------------------------------------------*/
// Blob转image
function blobToImage(blob, cb){
fileOrBlobToDataURL(blob, function (dataurl){
var img = new Image();
img.src = dataurl;
cb(img);
});
}
// image转Blob
function imageToBlob(src, cb){
imageToCanvas(src, function (canvas){
cb(dataURLToBlob(canvasToDataURL(canvas)));
});
}
/*-----------------------------------------------------------------------*/
// Blob转canvas
function BlobToCanvas(blob, cb){
fileOrBlobToDataURL(blob, function (dataurl){
dataURLToCanvas(dataurl, cb);
});
}
// canvas转Blob
function canvasToBlob(canvas, cb){
cb(dataURLToBlob(canvasToDataURL(canvas)));
}
/*-----------------------------------------------------------------------*/
// image转dataURL
function imageToDataURL(src, cb){
imageToCanvas(src, function (canvas){
cb(canvasToDataURL(canvas));
});
}
// dataURL转image，这个不需要转，直接给了src就能用
function dataURLToImage(dataurl){
var img = new Image();
img.src = d;
return img;
}
