Hi Simon. I made it!!!
After a lot of investigation I’ve successfully load the png. This is the
algoritm:
bool CTextureLoader::load(const char* fileName)
{
GLuint texture;
GLuint *theImage;
// Load Texture
SDL_Surface *image1;
SDL_RWops *rwop;
//--------------------------------------------------------------
// Aqui comprobar si la textura ya ha sido cargada
//-------------------------------------------------------------
// intentar cargar la imagen
if (!(image1 = IMG_Load(fileName)))
{
SDL_Quit();
exit(1);
}
// no estan soportadas las imagenes paletizadas
if (image1->format->palette)
{
SDL_Quit();
exit(1);
}
m_text_name = strdup(fileName);
theImage = (GLuint*)image1->pixels;
m_width = image1->w;
m_height = image1->h;
m_bitsPerPixel = image1->format->BitsPerPixel;
if (image1->format->BitsPerPixel == 24)
{
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
if (image1->format->Rshift < image1->format->Bshift) m_type
= GL_RGB;
else m_type = GL_BGR_EXT;
#else
if (image1->format->Rshift < image1->format->Bshift) m_type
= GL_BGR;
else m_type->format = GL_RGB;
#endif
}
// 32 bits texture format finder
else if (image1->format->BitsPerPixel == 32) {
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
if (image1->format->Rshift < image1->format->Bshift) m_type
= GL_RGBA;
else m_type = GL_BGRA_EXT;
#else
if (image1->format->Rshift < image1->format->Bshift) m_type
= GL_BGRA;
else m_type = GL_RGBA;
#endif
}
// unsupported texture format
else {
SDL_Quit();
exit(1);
}
// Create Texture
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture); // 2d texture (x and y
size)
m_texIndex = texture;
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); //
scale linearly when image bigger than texture
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); //
scale linearly when image smalled than texture
// 2d texture, level of detail 0 (normal), 3 components (red, green,
blue), x size from image, y size from image,
// border 0 (normal), rgb color data, unsigned byte data, and
finally the data itself.
glTexImage2D(GL_TEXTURE_2D, 0, 3, m_width, m_height, 0, m_type,
GL_UNSIGNED_BYTE, theImage);
// liberamos la memoria
SDL_FreeSurface(image1);
theImage = NULL;
}
//==========================================================================
Quick and dirty, I know, but it’s only a preview.
Thanks for all 
Ferran
|-----Mensaje original-----
|De: sdl-bounces+ferranferri=yahoo.es at libsdl.org [mailto:sdl-
|bounces+ferranferri=yahoo.es at libsdl.org] En nombre de Simon
|Enviado el: lunes, 24 de julio de 2006 1:46
|Para: A list for developers using the SDL library. (includes SDL-announce)
|Asunto: Re: [SDL] PNG + OpenGL problem
|
|> I?m trying to modify the nehe lesson 6 (SDL + OpenGL), but loading a PNG
|> image with SDL_image instead of use SDL. I can?t see correctly the
|> picture as texture.
|
|There’s a couple parts missing in your exercise, just to make sure
|you’re on the right track I’ll mention those parts here:
|
| 1) Load the image from disk to ram and be able to access the picture
|elements (getpixel(x,y), etc…)
| 2) Prepare the image data for OpenGL, sometimes the data must be
|re-aligned to fit the requirements of OpenGL. OpenGL likes to have a
|one-dimensionnal array of colors one after the other like this:
|
|unsigned char thePixels[256 * 256 * 4]; // This creates an array for an
|image of size 256x256 with 4 color components (RGBA).
|
|Then you put the information for opengl:
|thePixels[ x4 + y2564 + 0 ] = r; //red component of pixel at position
|(x,y)
|thePixels[ x4 + y2564 + 1 ] = g;
|thePixels[ x4 + y2564 + 2 ] = b;
|thePixels[ x4 + y2564 + 3 ] = a;
|
| 3) Once the data is ready you now need to upload it to opengl so that
|the texture is inside the video RAM. Uploading the image to opengl will
|also tell OpenGL how to display the image under certain circumstances
|(is it far away, really close). Functions to use: gluBuild2DMipmaps
|
| 4) Once the image is uploaded, you now need to enable textures, bind
|to the texture of your choice and render a quad with glTexCoord2f and
|also make sure you draw with color of (1,1,1) or the texture colors will
|be multiplied by the glColor3f().
|
|Finally, I did not find an error in the small bits of code you sent.
|However, I don’t suggest telling OpenGL to modify your image to make it
|correct, I would give a corrected image to opengl.
|
|And at last, when you have trouble with textures, it can be one of the
|following most of the time: black texture (are they enabled, bound
|correctly, uploaded at any time?), random color texture (trouble with
|the uploading, format doesn’t match, make sure your data is not RGBA
|when trying to upload for RGB). Sometimes the whole polygon is just one
|color, it might be because you didn’t not use the glTexCoord*() funcs
|correctly.
|
|HTH,
| Simon
|
|
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