Opengl ES 2.0 - Load PNG with GLKit instead of OpenGL API - opengl-es-2.0

Question

I have a piece of code that loads a textures using glTexImage2D like this:
// to test texturing
CGImageRef imageRef = [[UIImage imageNamed:#"Blob.png"] CGImage];
int width = CGImageGetWidth(imageRef);
int height = CGImageGetHeight(imageRef);
GLubyte* textureData = (GLubyte *)malloc(width * height * 4); // if 4 components per pixel (RGBA)
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(textureData, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);
glActiveTexture(GL_TEXTURE0);
glGenTextures(1, &texId);
glBindTexture(GL_TEXTURE_2D, texId);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_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_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, textureData);
glBindTexture(GL_TEXTURE_2D, 0);
I replaced the code with this, the code doesn throw any error but shows a black image instead.
NSError *error;
GLKTextureInfo *texture = [GLKTextureLoader textureWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"Blob.png" ofType:Nil]
options:Nil
error:&error]; assert(!error);
//bind the texture to texture unit 0
glActiveTexture(GL_TEXTURE0 + 0);
glBindTexture(texture.target, texture.name);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glEnable(texture.target);
glBindTexture(GL_TEXTURE_2D, 0);
What could be the problem?
The project I want to port is at https://github.com/glman74/simpleFBO

Answer 1

pathForResource:#"Blob.png" ofType:Nil
Should be
pathForResource:#"Blob" ofType:#"png"
And most of the time you should use nil instead if Nil

Answer 2

This is how I've solved it:
This goes in the OpenGL initialisation code
NSError *error;
GLKTextureInfo *texture = [GLKTextureLoader
textureWithContentsOfFile:
[[NSBundle mainBundle] pathForResource:#"Blob.png" ofType:Nil]
options:Nil
error:&error];
And this goes in the rendering method, in this case glkView:drawInRect:
glBindTexture(GL_TEXTURE_2D, 0);