Working Example of Parallel Processing?

[PeteMichaud]

I have had no luck at all searching google or github for a working example of a ParallelRowIterator in action. My goal is to loop through each pixel of a very large image and set all the values to something. How best to parallelize the operation? This would be great to add to the docs somewhere!

[PeteMichaud]

I'm trying to do something like:

Image<Rgb24> sourceImage = GetImage();
Image<Rgb24> outImage = GetImage();

for (var outY = 0; outY < outImage.Height; outY++)
{
    for (int outX = 0; outX < outImage.Width; outX++)
    {
        var outColor = GetArbitraryPixelFromAnywhereInsideSourceImage(sourceImage);
         outImage[outX, outY] = outColor;
    }
}

The main thing confusing me is the arbitrary access from the sourceImage. I can go row by row, pixel by pixel in the outImage, but I don't know what sourceImage row or column I'll need until I get inside this loop, and I will most of the time need to access not only a target pixel, but a sample of many of the pixels around it (eg. bicubic sampling).

I have working code that does this processing, but I can't figure out how to use the parallel access api to parallelize it, and just using Parallel.For scrambles the outImage (which I'm a little confused about actually, since each outPixel is an independent calculation and the sourceImage never changes).

[JimBobSquarePants]

I want to highlight here that you are misusing the Ideas discussion forum for questions.

There is no help category by design. This software is released AS IS unless you purchase a Six Labors License. Alternatively you can ask on Stack Overflow and maybe a community member will prvide an answer.

[PeteMichaud]

Sorry @JimBobSquarePants, my mistake. I just came here from the link in the top level readme where it says:

Do you have questions? We are happy to help! Please join our Discussions Forum, or ask them on Stack Overflow using the ImageSharp tag. Please do not open issues for questions.

So I thought it was the right place.

[JimBobSquarePants]

Our bad, I've updated the readme. I'll answer over at SO

[PeteMichaud]

Anyway, I posted the question here for future reference: https://stackoverflow.com/questions/71388492/right-way-to-parallelize-pixel-access-across-multiple-images-using-imagesharp