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    <p>If you read the color values as strings from an array for each pixel it does not really matter what technique you use as the bottleneck would be that part right there.</p> <p>For each pixel the cost is split on (roughly) these steps:</p> <ul> <li>Look up array (really a node/linked list in JavaScript)</li> <li>Get string</li> <li>Pass string to fillStyle <ul> <li>Parse string (internally) into color value</li> </ul></li> <li>Ready to draw a single pixel</li> </ul> <p>These are very costly operations performance-wise. To get it more efficient you need to convert that color array into something else than an array with strings ahead of the drawing operations.</p> <p>You can do this several ways:</p> <ul> <li>If the array comes from a server try to format the array as a blob / typed array instead before sending it. This way you can copy the content of the returned array almost as-is to the canvas' pixel buffer.</li> <li>Use a web workers to parse the array and pass it back as a transferable object which you them copy into the canvas' buffer. This can be copied directly to the canvas - or do it the other way around, transfer the pixel buffer to worker, fill there and return.</li> <li>Sort the array by color values and update the colors by color groups. This way you can use fillStyle or calculate the color into an Uint32 value which you copy to the canvas using a Uint32 buffer view. This does not work well if the colors are very spread but works ok if the colors represent a small palette.</li> </ul> <p>If you're stuck with the format of the colors then the second option is what I would recommend primarily depending on the size. It makes your code asynchronous so this is an aspect you need to deal with as well (ie. callbacks when operations are done).</p> <p>You can of course just parse the array on the same thread and find a way to camouflage it a bit for the user in case it creates a noticeable delay (900x900 shouldn't be that big of a deal even for a slower computer).</p> <p>If you convert the array convert it into unsigned 32 bit values and store the result in a Typed Array. This way you can iterate your canvas pixel buffer using Uint32's instead which is much faster than using byte-per-byte approach.</p>
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