iOS Loading png images...

[Soulstorm]

I am using the following code to load png textures:

- (void)loadTexture:(NSString *)name intoLocation:(GLuint)location {
	
	CGImageRef textureImage = [UIImage imageNamed:name].CGImage;
	if (textureImage == nil) {
        NSLog(@"Failed to load texture image");
		return;
    }
	
    NSInteger texWidth = CGImageGetWidth(textureImage);
    NSInteger texHeight = CGImageGetHeight(textureImage);
	
	GLubyte *textureData = (GLubyte *)malloc(texWidth * texHeight * 4);
	
    CGContextRef textureContext = CGBitmapContextCreate(textureData,
														texWidth, texHeight,
														8, texWidth * 4,
														CGImageGetColorSpace(textureImage),
														kCGImageAlphaPremultipliedLast);
	
	// Rotate the image
	CGContextTranslateCTM(textureContext, 0, texHeight);
	CGContextScaleCTM(textureContext, 1.0, -1.0);
	
	CGContextDrawImage(textureContext, CGRectMake(0.0, 0.0, (float)texWidth, (float)texHeight), textureImage);
	CGContextRelease(textureContext);
	
	glBindTexture(GL_TEXTURE_2D, location);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texWidth, texHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureData);
	
	free(textureData);
	
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
}

The problem is that although the image is loaded correctly in some situations, it does not work on others on PNG images. Sometimes they are displayed as a white area. I am including 2 png images. The first one works, and the second doesn't.

Any ideas on what may be wrong?

 

[kainjow]

Does the second one have alpha values? If so you need to setup the blending options in OpenGL. This is something I used in a recent (Mac) project (note: I'm an OpenGL newbie):

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

...

glDisable(GL_BLEND);

 

[Soulstorm]

Does the second one have alpha values? If so you need to setup the blending options in OpenGL. This is something I used in a recent (Mac) project (note: I'm an OpenGL newbie):

glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

...

glDisable(GL_BLEND);

Actually is was a matter of OpenGL's limitation that commands using textures that have a power of 2.

But how can I bypass that limitation?