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Editorial Team
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Asked: 2026-05-13T18:23:28+00:00

Ok, what I’m trying to achieve is to load an image as a single

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Ok, what I’m trying to achieve is to load an image as a single resource and then save different parts of it as a number of different textures (basically chopping the image into smaller squares and then saving them separately).

For my game, simply mapping different sections of the original image to my shapes won’t work and being able to have each ’tile’ as a separate texture would be awesome.

Below is the code I’m using for my texture loader. I’ve tried messing round with the width and height of the texture being loaded but getting some weird results.

Any suggestions would be much appreciated.

Thanks 

glBindTexture(GL_TEXTURE_2D, texture[0]);   

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

NSString *path =
      [[NSBundle mainBundle] pathForResource:@"checkerplate" ofType:@"png"];
NSData *texData = [[NSData alloc] initWithContentsOfFile:path];
UIImage *image = [[UIImage alloc] initWithData:texData];

GLuint width = CGImageGetWidth(image.CGImage);
GLuint height = CGImageGetHeight(image.CGImage);    
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( height * width * 4 );
CGContextRef context = CGBitmapContextCreate( 
      imageData, width, height, 8, 4 * width, colorSpace,
      kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
CGColorSpaceRelease( colorSpace );
CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
CGContextTranslateCTM( context, 0, height - height );
CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA,
      GL_UNSIGNED_BYTE, imageData);

CGContextRelease(context);

free(imageData);
[image release];
[texData release];
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1 Answer

  1. Editorial Team

    Ok, just in case anyone wants to achieve this, i figured it out. All you need to do is modify the line CGContextDrawImage and alter the width and height parameters.

    This results in the whole texture being loaded in but then will only draw the area specified on this line.

    Basically,

    CGContextDrawImage( context, CGRectMake(0, 0, width*2, height*2 ), image.CGImage );

    will draw 1/4 of the image (as its height and width are being doubled past the textures size).

    🙂

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