Bitmap rendering could be sped up

[prydin]

I'm working on code that dynamically builds a bitmap every frame. I can du this by generating a native Go image.RGBA, then use PictureDataFromImage, turn it into a sprite and draw it to my canvas. Doing that, my pixels are copied at least three times. I could speed it up by building my own PictureData without taking the extra step via an Image. However, my profiling shows that I still spend a considerable amount of time in NewGLPicture.

I could easily build my image as a flat array of uint8 which could be mapped directly to a Texture.

For this, I propose we either introduce a FlatArrayPicture type that simply contains a flat array of uint8 that NewGLPicture can just map to the texture - or - that we expose the underlying Texture object so code that needs to render bitmaps VERY quickly can access them directly.

I am willing to make this any of these changes in a PR.

[cebarks]

Unless I'm misunderstanding your usecase, I think the functionality you want already exists in the glhf backend that Pixel uses. Specifically looking at glhf.NewTexture(), which allows you to build a new texture from an array of uint8. Not sure how you would render that as opengl confuses me to no end. Otherwise, you can access the glhf.Texture of a pixel.Canvas with the .Texture() method.

[prydin]

Yeah, I eventually figured that out. There's still a few copies made internally in the code that could you probably avoid, but I'm getting the performance I need out of it now, so I'm closing this.