Question

I am creating a 2D openGL texture from an NSImage (cocoa desktop).
I grabbed some code from the internet and it seems to work.

However, I started to insert calls to glGetError() here and there to track other rendering bugs, and thus I traced a GL_INVALID_ENUM error to the call mentioned above. As per the documentation on glTexParameteri, both GL_TEXTURE_2D and GL_TEXTURE_BORDER seem to be valid parameters…?

any clue?

this is the code:

- (void) createOpenGLTexture
{
[_openGLContext makeCurrentContext];


if (_textureID != 0) {
    glDeleteTextures(1, &_textureID);
    _textureID = 0;
}

NSSize imageSize = [_originalImage size];


// .............................................................
// Flip Image Vertically

NSImage* image = [[NSImage alloc] initWithSize:imageSize];


NSRect rect = NSMakeRect(0, 0, imageSize.width, imageSize.height);

[image lockFocus];

NSAffineTransform* transform = [NSAffineTransform transform];
[transform translateXBy:0 yBy:rect.size.height];
[transform scaleXBy:+1.0 yBy:-1.0];
[transform concat];
[_originalImage drawAtPoint:NSZeroPoint 
                   fromRect:rect 
                  operation:NSCompositeCopy 
                   fraction:1];
[image unlockFocus];


// Then we grab the raw bitmap data from the NSBitmapImageRep that is 
// the ‘source’ of an NSImage

NSBitmapImageRep* bitmap = [[NSBitmapImageRep alloc] initWithData:[image TIFFRepresentation]];
[image release];


GLenum   imageFormat = GL_RGBA;

imageSize = [bitmap size];  // Needed?

long sourceRowBytes = [bitmap bytesPerRow];

//  This SHOULD be enough but nope
GLubyte* sourcePic = (GLubyte*) [bitmap bitmapData];

//  We have to copy that raw data one row at a time….yay
GLubyte* pic = malloc( imageSize.height * sourceRowBytes );
GLuint  i;
GLuint intHeight = (GLuint) (imageSize.height);

for (i = 0; i < imageSize.height; i++) {
    memcpy(pic + (i * sourceRowBytes), 
           sourcePic + (( intHeight - i - 1 )*sourceRowBytes), 
           sourceRowBytes);
}

[bitmap release];

sourcePic = pic;


// .........................................................................
// Create the texture proper

glEnable(GL_TEXTURE_2D);
checkOpenGLError();

glEnable(GL_COLOR_MATERIAL);
checkOpenGLError();

glGenTextures (1, &_textureID);
checkOpenGLError();

glBindTexture (GL_TEXTURE_2D, _textureID);
checkOpenGLError();

glPixelStorei(GL_UNPACK_ALIGNMENT,1);
checkOpenGLError();

//  Here we set the basic properties such as how it looks when resized and if it's bordered
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BORDER, 0);
checkOpenGLError();

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

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
checkOpenGLError();

//  Not really necessary all the time but we can also define if it can be tiled (repeating)
//  Here GL_TEXTURE_WRAP_S = horizontal and GL_TEXTURE_WRAP_T = vertical
//  This defaults to GL_REPEAT so we're going to prevent that by using GL_CLAMP
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
checkOpenGLError();

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
checkOpenGLError();

//  And.....CREATE
glTexImage2D(GL_TEXTURE_2D, 
             0, 
             imageFormat, 
             rect.size.width, 
             rect.size.height, 
             0, 
             imageFormat, 
             GL_UNSIGNED_BYTE, 
             sourcePic);
checkOpenGLError();

glDisable(GL_TEXTURE_2D);
checkOpenGLError();

glDisable(GL_COLOR_MATERIAL);

checkOpenGLError();
}

Answer 1

GL_TEXTURE_BORDER is not a valid enum for glTexParameter(). Reference: http://www.opengl.org/sdk/docs/man/xhtml/glTexParameter.xml

You cannot (and don’t need to) specify the bordersize. GL_TEXTURE_BORDER is only a valid enum for glGetTexLevelParameter() to retrieve the bordersize the opengl driver assigned to a specific texture level. As far as I am aware this is not used any more and the function returns 0 on all newer systems.

Don’t confuse it with GL_TEXTURE_BORDER_COLOR which is used to set the color rendered when using the GL_CLAMP_BORDER wrapping mode.