Multiple readback operations can be made faster.

Hi there, just working on a Quagga2-based product, and came across this warning in the dev tools. Is there a reason that this is not changed/implemented for performance?

Canvas2D: Multiple readback operations using getImageData are faster with the willReadFrequently attribute set to true. [quagga.min.js:3]

[sam-the-programmer]

Thanks

[ericblade]

I haven’t ever seen that, and had no idea of it’s existence.

A boolean value that indicates whether or not a lot of read-back operations are planned. This will force the use of a software (instead of hardware accelerated) 2D canvas and can save memory when calling [getImageData()](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/getImageData) frequently.

It does look like getImageData is used every frame grab, which might perhaps make a difference there, though it might be rather hard to quantify.

My guess would be that either that option didn’t exist when this code was originally written, was not known by the original author, or was determined to not be helpful?

i real quick traced out the probably relevant getImageData triggering that to frame_grabber_browser … not sure exactly where the relevant getContext(‘2d’) call is though.

I’ll try to take a deeper look at it next time i’ve got some time to work on this, i always like easy performance improvements 😃