Re: How to Grayscale Texture

It's that move from GPU to RAM that is costly, not the function.

SDL_gpu has a shader interface that would make this a snap.

Jonny D


On Tue, Jul 26, 2016 at 10:55 AM, ancientcc <[email protected]> wrote:

> I give an example of use: 1)Generate tow texture from tow *.png file, 2)Use
> SDL_RenderCopy, generate new texture base on these tow texture. 3)Need
> grayscale the new texture.
>
>  I have a question, to above case, even use SDL_TEXTUREACCESS_STREAMING, it
> require move pixels data from VRAM to system memory. In order to move, is
> there method except SDL_RenderReadPixels?
>
> -----Original Message-----
> 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.
>
>
> --
> //David Olofson - Consultant, Developer, Artist, Open Source Advocate
>
> .--- Games, examples, libraries, scripting, sound, music, graphics ---.
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