16 bits textures and SDL

SDL Development
1

Hello,

I have a probleme using SDL to load 16 bits textures
:frowning:
I searched over google many hours but didn’t find
anything…
Maybe some people on this list encountered the same
problem ?

Here is the code (the loaded texture is a power of 2
one (256*256) and this code works when changed for
loading 32 bits textures) :

SDL_Surface *image;
SDL_Surface *newImage;
GLubyte *dataImage;
GLuint texImage;

int bpp=16;

image = IMG_Load(path);

newImage = SDL_CreateRGBSurface(SDL_SWSURFACE, 256,
256, bpp,
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
0xf000, 0x0f00, 0x00f0, 0x000f);
#else
0x000f, 0x00f0, 0x0f00, 0xf000);
#endif

int resultBlit = SDL_BlitSurface(image, NULL,
newImage, NULL);

dataImage = (GLubyte *)malloc((bpp/8)256256);
memcpy(dataImage, newImage->pixels, ((bpp/8)256256)
);

glGenTextures(1, &texImage);
glBindTexture(GL_TEXTURE_2D, texImage);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_LINEAR);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
GL_CLAMP_TO_EDGE);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA4, 256, 256, 0,
GL_RGBA, GL_UNSIGNED_BYTE, dataImage);

The program hangs at “glTexImage2D”.

Thanks for your help ;)___________________________________________________________
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2

gamedev srt wrote:

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA4, 256, 256, 0,
GL_RGBA, GL_UNSIGNED_BYTE, dataImage);

Using GL_RGBA, GL_UNSIGNED_BYTE means that you’re telling OpenGL to read
4 unsigned bytes per pixel (RGBA8). But your SDL surface is in RGBA4
format. So you need something like :

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA4, 256, 256, 0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, dataImage);

GL_RGBA4 is just OpenGL’s internal texture format (ie how the texture is
stored on your video card).

Stephane

3

Hello St?phane,

Thanks very much for your help, now there’s no more
crashes :wink:

The only remaini!ng problem is that images have wrong
colors, in fact they appear like if i added a blue
filter on my screen. For exemple, white color appear
blue :frowning:

Any clues ?> Using GL_RGBA, GL_UNSIGNED_BYTE means that you’re

telling OpenGL to read
4 unsigned bytes per pixel (RGBA8). But your SDL
surface is in RGBA4
format. So you need something like :

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA4, 256, 256,
0, GL_RGBA, GL_UNSIGNED_SHORT_4_4_4_4, dataImage);

GL_RGBA4 is just OpenGL’s internal texture format
(ie how the texture is
stored on your video card).

Stephane

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