Something is wrong with converting SDL surface to GL texture
I can't find my error, why wasn't the text generated? When using texture instead of text I get nothing or black background with colored dots please help
GLuint texture;
SDL_Surface *text = NULL;
TTF_Font *font = NULL;
SDL_Color color = {0, 0, 0};
font = TTF_OpenFont("../test.ttf", 20);
text = TTF_RenderText_Solid(font, "Hello, SDL !!!", color);
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, text->w, text->h, 0, GL_RGB, GL_UNSIGNED_BYTE, text->pixels);
SDL_FreeSurface(text);
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2 answers
A Few Things You Should Check First
- Is the font loaded correctly? check if "font == NULL" is probably your wrong font path
- is the shader being used correctly (if you are using a shader)?
I am assuming you have set the wrong pixel format type in glTexImage2D so that random colored dots appear on your texture
Below is my code loading an image via SDL_image to use OpenGL, I think it would be a good start to figure out which step you missed or forgot.
By the way, this code is not perfect. The pixel format type is greater than four (like index color) and I only handle a few of them.
/*
* object_, originalWidth_ and originalHeight_ are private variables in
* this class, don't panic.
*/
void
Texture::Load(string filePath, GLint minMagFilter, GLint wrapMode)
{
SDL_Surface* image;
GLenum textureFormat;
GLint bpp; //Byte Per Pixel
/* Load image file */
image = IMG_Load(filePath.c_str());
if (image == nullptr) {
string msg("IMG error: ");
msg += IMG_GetError();
throw runtime_error(msg.c_str());
}
/* Find out pixel format type */
bpp = image->format->BytesPerPixel;
if (bpp == 4) {
if (image->format->Rmask == 0x000000ff)
textureFormat = GL_RGBA;
else
textureFormat = GL_BGRA;
} else if (bpp == 3) {
if (image->format->Rmask == 0x000000ff)
textureFormat = GL_RGB;
else
textureFormat = GL_BGR;
} else {
string msg("IMG error: Unknow pixel format, bpp = ");
msg += bpp;
throw runtime_error(msg.c_str());
}
/* Store widht and height */
originalWidth_ = image->w;
originalHeight_ = image->h;
/* Make OpenGL texture */
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &object_);
glBindTexture(GL_TEXTURE_2D, object_);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minMagFilter);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, minMagFilter);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapMode);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapMode);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexImage2D(
GL_TEXTURE_2D, // texture type
0, // level
bpp, // internal format
image->w, // width
image->h, // height
0, // border
textureFormat, // format(in this texture?)
GL_UNSIGNED_BYTE, // data type
image->pixels // pointer to data
);
/* Clean these mess up */
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_TEXTURE_2D);
SDL_FreeSurface(image);
}
For more information, you should check out the SDL wiki or deep into its source code to fully understand the SDL_Surface architecture.
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