Re: Bug in SDL_CreateTextureFromSurface ?

Hi,

I don't think this is a bug: SDL_CreateTextureFromSurface() converts the 
pixels to a format best suited for the renderer.

Also, note how SDL_UpdateTexture() does *not* take a SDL_Surface as 
input, but a void pointer to "raw pixel data".
This means the function does not "know" how to convert image surface to 
the internally used format.
Maybe use SDL_QueryTexture() to get the texture's raw format and convert 
your surface to that?
(I don't think you can expect your currently commented out code to 
always work, as the render is not guaranteed to support any specific 
pixelformat you might set in SDL_CreateTexture())

Cheers,
Daniel

On 21.11.2016 09:06, zweifel wrote:
> Hi,
>
> I loaded an image which the pixel format is ABGR. However, it seems that
> when I create a texture from a surface SDL2 does not keep the format of
> the surface. And therefore, if I try to update it later with
> SDL_UpdateTexture() I get inverted red and blue channels (i.e., it seems
> to think the image is in ARGB format).
> I had to use SDL_CreateTexture and explicitly set the format for it to
> work as expected.
>
> If anybody can confirm this I will file a bug.
>
> The code is as follows. By changing the way the texture is made, the
> final result changes.
>
>
>
>
>
>
>
>
> Code:
>
>
> #include"SDL2/SDL.h"
> #include"SDL2/SDL_image.h"
> #include
>
> int main(int argc, char** argv)
> {
>    bool quit= false;
>    int filter_size=2;
>
>    SDL_Event event;
>
>    SDL_Init(SDL_INIT_VIDEO);
>
>    SDL_Surface* image= IMG_Load("image3.png");
>    int image_height=image->h;
>    int image_width=image->w;
>    int bpp = (int) image->format->BytesPerPixel;
>    std::cout << "Bpp " << bpp << "Size "<< image->w << image->h <<
> std::endl;
>    SDL_PixelFormat* pixel_format = image->format;
>    Uint32 pixelFormatEnum = pixel_format->format;
>    const char* surface_pixel_format =
> SDL_GetPixelFormatName(pixelFormatEnum);
>    std::cout << "Format " << surface_pixel_format << std::endl;
>
>
>    SDL_Window* window= SDL_CreateWindow("Convolution",
> SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, image_width/2,
> image_height/2, 0);
>
>    SDL_Renderer* renderer= SDL_CreateRenderer(window, -1, 0);
>
>
>
>    SDL_Texture* texture= SDL_CreateTextureFromSurface(renderer, image);
>
>    //SDL_Texture* texture= SDL_CreateTexture(renderer,
> SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STREAMING, image->w, image->h);
>
>
>    SDL_UpdateTexture(texture, NULL, image->pixels, image->pitch);
>
>    //SDL_LockTexture(texture, NULL, &image->pixels, &image->pitch);
>    //SDL_UnlockTexture(texture);
>
>    while(!quit)
>    {
>
>
>       SDL_WaitEvent(&event);
>
>       switch(event.type)
>       {
>          case SDL_QUIT:
>          {
>             quit=true;
>          }
>          break;
>       }
>
>       SDL_RenderCopy(renderer, texture, NULL, NULL);
>       SDL_RenderPresent(renderer);
>    }
>
>    SDL_DestroyTexture(texture);
>    SDL_FreeSurface(image);
>    SDL_DestroyRenderer(renderer);
>    SDL_DestroyWindow(window);
>
>    SDL_Quit();
>
>    return 0;
> }
>
>
>
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