Re: How to Grayscale Texture

On Tue, Jul 26, 2016 at 1:10 PM, ancientcc <[email protected]> wrote:
> Would like to use SDL_Texture widely in code, but SDL_RenderReadPixel is too
> low, require grayscale texture directly. How to do?
[...]

Is this something that needs to be done in real time, or can you
preprocess the graphics at load time?

If it needs to be real time, you should use procedural textures, using
an SDL_Surface or a raw buffer as source data. (See
SDL_TEXTUREACCESS_STREAMING.)

You should absolutely not use SDL_RenderReadPixels(), ever, for
anything other than screenshots and the like. It's typically faster to
do all rendering in software, just to avoid ever moving data from VRAM
to system memory. :-)

If you want it all really fast and accelerated, you probably need to
use custom shaders, but AFAIK, that's not directly supported by the
SDL 2D API, so you'd have to move to OpenGL or Direct3D.


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