Is it possible storing drawn graphics into temp bitmap for later alpha composition on HTML5 canvas?
I'm making some kind of UI layers with HTML5 canvas. All layers can开发者_C百科 be nested and can have alpha. Nested layers should be drawn with correct alpha composition. To do this, some kind of temporary bitmap storage is required. How can I store graphics drawing into temp bitmap?
You can always make a canvas in memory (as in not add it to the DOM)
storedCanvas = document.createElement('canvas');
Then you can paint an entire canvas to that canvas:
storedCtx.drawImage(firstCanvas, 0, 0);
Then you can do whatever you want to the first canvas, the stored one won't change. Then, when you want to recall that, you just do
firstCanvasCtx.drawImage(storedCanvas, 0, 0);
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