![]() Your paw and the yellow background will show through the transparent center of your frame. Set compositing back to the default source-over so new drawings will be drawn on top of existing drawings.ĭraw your frame that's transparent in the center. Your paw will not be overwritten because new (yellow) pixels will be drawn "under" your paw. Set compositing to destination-over so new drawings will be drawn under existing pixels.įill the yellow box. This causes your paw to be recolored because the newly colored rectangle pixels will only appear where your paw pixels currently exist. Set compositing to source-atop so new drawings will only be drawn where the existing paw pixels exist.įill the canvas with your new paw color using fillStyle & fillRect. You cannot directly change the color of anything previously drawn on the canvas, so the typical workflow of canvas is to erase it and redraw items in their new positions & colors. Here's how to use compositing to change the color of your paw.Ĭlear the canvas. first draw a blue destination rectangleĬtx.globalCompositeOperation='destination-over' 'destination-over' compositing will draw new pixels under the existing canvas pixels. (red will overwrite only where it overlapped the blue) they overlap the existing blue pixels)Ĭtx.globalCompositeOperation='source-atop' (the new red pixels will only be drawn where first draw a blue destination rectangle 'source-atop' compositing will draw new pixels only where the new pixels overlap the existing canvas pixels. The default method of compositing is 'source-over' where new drawings are drawn over existing pixels. In your case, 3 compositing modes are useful to learn. ![]() I have created a fiddle just to enlighten you with my question.Ĭompositing tells the canvas what to do when drawing additional new drawings (pixels) on the canvas. I should be able to fill the paw image in the middle as well and not just the main image. ![]() i would like to customize the color of this too should I declare something like this again? try changing this to see the effectĬtx.fillRect(40,0,250,300) // not sure if there's other way to fill in the tranparent area. JS: var can = document.getElementById('canvas1') Ĭtx.fillStyle = 'yellow' // background color. This is my current code (with fiddle here too): There will be 2 image files only, Image 1 and Image 2: To further understand my question, I created an illustration. But, I will have more than one, in other words, overlapping images. My problem is, I have to modify the colors of the images in the canvas. It's my first time to use html5 canvas and I have no idea yet how it works.
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