I'm trying to put image in clipboard when user copies canvas selection:
So I thought the right way would be to convert canvas tu dataURL, dataURL to blob and blob to binary string.
Theoretically it should be possible to skip the blob, but I don't know why.
So this is what I did:
function copy(event) {
console.log("copy");
console.log(event);
//Get DataTransfer object
var items = (event.clipboardData || event.originalEvent.clipboardData);
//Canvas to blob
var blob = Blob.fromDataURL(_this.editor.selection.getSelectedImage().toDataURL("image/png"));
//File reader to convert blob to binary string
var reader = new FileReader();
//File reader is for some reason asynchronous
reader.onloadend = function () {
items.setData(reader.result, "image/png");
}
//This starts the conversion
reader.readAsBinaryString(blob);
//Prevent default copy operation
event.preventDefault();
event.cancelBubble = true;
return false;
}
div.addEventListener('copy', copy);
But when the DataTransfer
object is used out of the paste
event thread the setData
has no longer any chance to take effect.
How can I do the conversion in the same function thread?
Here is a hacky-way to get you synchronously from a blob to it's bytes. I'm not sure how well this works for any binary data.
function blobToUint8Array(b) {
var uri = URL.createObjectURL(b),
xhr = new XMLHttpRequest(),
i,
ui8;
xhr.open('GET', uri, false);
xhr.send();
URL.revokeObjectURL(uri);
ui8 = new Uint8Array(xhr.response.length);
for (i = 0; i < xhr.response.length; ++i) {
ui8[i] = xhr.response.charCodeAt(i);
}
return ui8;
}
var b = new Blob(['abc'], {type: 'application/octet-stream'});
blobToUint8Array(b); // [97, 98, 99]
You should consider keeping it async but making it two-stage, though, as you may end up locking up the browser.
Additionally, you can skip Blobs entirely by including a binary-safe Base64 decoder, and you probably don't need to go via Base64 AND Blob , just one of them.
Blob can be converted to binary string by getting Blob as d ataURI and then applying atob
. This, however, again [requires FileReader][3]
. In my case, it's best to skip the blob alltogether:
//Canvas to binary
var data = atob(
_this.editor.selection.getSelectedImage() //Canvas
.toDataURL("image/png") //Base64 URI
.split(',')[1] //Base64 code
);
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