71² – The ramblings of two 30-something developers

// Set the OGL context and make it current
[[self openGLContext] makeCurrentContext];

// Set the OGL clear color
glClearColor(0, 0, 0, 1);

// This controls how a texture is blended with other textures
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_ALPHA);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glMatrixMode(GL_TEXTURE);
glLoadIdentity();
glRotatef(90, 0, 0, 1);

// Set up the OGL projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 320, 0, 480, -1, 1);
glViewport(0, 0, self.bounds.size.width, self.bounds.size.height);

// Set up the modelview matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

// Enable the OGL and client states we are going to need
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);

}

// Grab the width and height of the image and also set the content size
width = CGImageGetWidth(image);
height = CGImageGetHeight(image);
contentSize = CGSizeMake(width, height);

// Even though NVidia can handle NPOT textures, ATI X1600 cards cannot, so we are making
// all textures POT to compensate for this.
NSUInteger pot; // Holds the power of 2 value being calculated

width = contentSize.width;
if((width != 1) && (width & (width – 1))) {
pot = 1;
while( pot < width)
pot *= 2;
width = pot;
}

height = contentSize.height;
if((height != 1) && (height & (height - 1))) {
pot = 1;
while(pot < height)
pot *= 2;
height = pot;
}

// Calculate the texture ratio
textureRatio.width = 1.0f / (float)width;
textureRatio.height = 1.0f / (float)height;

// Allocate storage for the image data
GLubyte *data = calloc(width * height * 4, sizeof(GLubyte));

// Create a color space that will be used when we render our image into the context
CGColorSpaceRef color_space = CGColorSpaceCreateDeviceRGB();

// We need to lock the current OGL context before creating a bitmap context to render to. Not
// doing so can cause the threads to mutex. The current context is held in glview so we use the
// appdelegate to grab glview
ParticleDesignerAppDelegate * appDelegate = [[NSApplication sharedApplication] delegate];

// Set the current openGL context
NSOpenGLContext *currentContext = [appDelegate.glview openGLContext];
CGLLockContext([currentContext CGLContextObj]);
[currentContext makeCurrentContext];

// Create a context into which we will render the image
CGContextRef context = CGBitmapContextCreate(
data,
width,
height,
8,
width * 4,
color_space,
kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host);

// Move the images origin and flip it so that it is not upside down
CGContextTranslateCTM(context, 0.0, height);
CGContextScaleCTM(context, 1.0, -1.0);

// Render the image to the context
CGContextDrawImage(context, CGRectMake(0, 0, width, height), image);

// Generate an OGL texture and copy the image data from our context into it
glGenTextures(1, &name);
glBindTexture(GL_TEXTURE_2D, name);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, data);

// Set up the texture parameters
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, aFilter);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, aFilter);
glBindTexture(GL_TEXTURE_2D, 0);

// Unlock the context now we have finished creating our texture
CGLUnlockContext([currentContext CGLContextObj]);

// Release the memory we have used
CFRelease(context);
CFRelease(color_space);
free(data);

DLog(@"INFO - Texture2D: Created texture name: %i", name);

// Return the name of the texture we have just created
return name;
}

// Bottom Right
glVertex2f(164, 0);
glTexCoord2f(1, 0);

// Top Right
glVertex2f(164, 64);
glTexCoord2f(1, 1);

// Top Left
glVertex2f(100, 64);
glTexCoord2f(0, 1);
glEnd();