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Development => Programming => Topic started by: reaver on July 22, 2014, 08:08:49 AM

Title: SDL2 getting pixel data from a texture
Post by: reaver on July 22, 2014, 08:08:49 AM

Not sure if I'm missing something obvious, but I can't find any API whatsoever to help me with getting the pixels from a static texture, so that I can save them to file.
I can create a render target and copy the texture to the rendertarget, but then again I can't find any way to get the pitch which is needed to read the texture pixels. That's ludicrous! Never mind the fact that people have said that SDL_RenderReadPixels() has been buggy and only gets pixels from the window, even if you set the rendertarget to be a texture..

Title: Re: SDL2 getting pixel data from a texture
Post by: Cfyz on July 22, 2014, 11:57:48 AM

Maybe this will help: Stack Exchange - How do I access the pixels of an SDL 2 texture? (http://gamedev.stackexchange.com/questions/62705/how-do-i-access-the-pixels-of-an-sdl-2-texture)

Title: Re: SDL2 getting pixel data from a texture
Post by: reaver on July 22, 2014, 12:02:51 PM

Thanks, but nope :)
This solution requires the texture to be created as streaming and I do not want that.

Title: Re: SDL2 getting pixel data from a texture
Post by: Cfyz on July 22, 2014, 12:27:27 PM

Quote from: reaver

I can't find any way to get the pitch which is needed to read the texture pixels.

A brief peek into SDL2 sources revealed that this pitch parameter tells SDL the width of a single line in your buffer, in bytes. SDL copies the data to your buffer line-by-line, incrementing the pointer by that value.

Title: Re: SDL2 getting pixel data from a texture
Post by: reaver on July 22, 2014, 02:45:02 PM

Ok, yeah, apparently the only sure way is copy to rendertarget and readpixels(), but readpixels() is broken and tries to use the backbuffer instead of the rendertarget. Awesome. Perhaps I need to ditch SDL2, if it can't do correctly something as basic as this.

UPDATE: ok, actually readpixels() works using the OpenGL driver instead of the default D3D9 one.

Title: Re: SDL2 getting pixel data from a texture
Post by: Krice on April 19, 2016, 11:01:01 AM

Quote from: reaver on July 22, 2014, 02:45:02 PM

ok, actually readpixels() works using the OpenGL driver instead of the default D3D9 one.

Is this still true? I'm trying to save a piece of screen with SDL_RenderReadPixels, but it's crashing for some reason. In some cases saving the background is just a feature you need (if you have a window or menu pop on previous graphics).

Title: Re: SDL2 getting pixel data from a texture
Post by: abraksil on April 23, 2016, 09:39:59 PM

Woow haven't used SDL for quite some  time now. Didn't new there was 2.0.

Title: Re: SDL2 getting pixel data from a texture
Post by: Krice on April 24, 2016, 07:39:31 AM

Quote from: abraksil on April 23, 2016, 09:39:59 PM

Didn't new there was 2.0.

No, it's 2.0.4.