macOS Can't Use PNG For OpenGL Textures

[davbeck]

I am trying to figure out this crazy world of OpenGL, specifically on mac and iphone.

I have a function that takes a path to a image and turns it into an opengl texture. bmp seems to work fine but not png. The problem is that when I use NSBitmapImageRep to get the pixel data which represents it as having one pane. the cautionary if statement blocks any weird stuff from happening.

- (void)textureFromPath:(NSString *)path textureID:(GLuint *)texName {
	NSBitmapImageRep *bitmap = [NSBitmapImageRep imageRepWithContentsOfFile:path];
    int samplesPerPixel = 0;
	
	//glPixelStorei(GL_UNPACK_ROW_LENGTH, [bitmap pixelsWide]); // 4
    //glPixelStorei(GL_UNPACK_ALIGNMENT, 1); // 5
    if (*texName == 0)
		glGenTextures (1, texName);
	
	glBindTexture(GL_TEXTURE_2D, *texName);
    //glBindTexture(GL_TEXTURE_RECTANGLE_ARB, *texName);
	
	glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
                    GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    samplesPerPixel = [bitmap samplesPerPixel];
	
	if(![bitmap isPlanar] &&
       (samplesPerPixel == 3 || samplesPerPixel == 4)) {
        glTexImage2D(GL_TEXTURE_2D,		//GL_TEXTURE_RECTANGLE_ARB,
                     0,
                     samplesPerPixel == 4 ? GL_RGBA8 : GL_RGB8,
                     [bitmap pixelsWide],
                     [bitmap pixelsHigh],
                     0,
                     samplesPerPixel == 4 ? GL_RGBA : GL_RGB,
                     GL_UNSIGNED_BYTE,
					 [bitmap bitmapData]);
    }
	[bitmap release];
}

 

[kainjow]

Not sure about the png issue, but the [bitmap release] is incorrect as bitmap is an autoreleased object and calling release without a retain will cause it to crash later when it gets released by the autorelease pool.

 

[davbeck]

Now that you mention it, it should crash later but it doesn't. curious.

I have attached an example of what happens when I try to bring in a png.

 

[kainjow]

This thread might be of help:
http://www.idevgames.com/forum/showthread.php?t=13452

 

[lazydog]

Hi
It looks to me like your image needs to be inverted… OpenGL uses the bottom left corner as ( 0, 0 ). The shearing effect might be because your image is using padding bytes at the end of each row, or the dimensions aren't a power of two.

b e n

 

[davbeck]

Why would the dimensions need to be power of two? That seems like a huge disadvantage.

 

[davbeck]

I finally got it working using imageio. I am posting the function for future generations.

- (void)textureFromPath:(NSString *)path textureID:(GLuint *)texName {
	CFURLRef url = CFURLCreateWithFileSystemPath(NULL, path, kCFURLPOSIXPathStyle, NO);
        //xCode troughs a warning about using NSString instead of CFString but since they are compatible it works anyway.
	
	CGImageSourceRef myImageSourceRef = CGImageSourceCreateWithURL(url, NULL);
	CGImageRef myImageRef = CGImageSourceCreateImageAtIndex (myImageSourceRef, 0, NULL);
	size_t width = CGImageGetWidth(myImageRef);
	size_t height = CGImageGetHeight(myImageRef);
	
	CGRect rect = {{0, 0}, {width, height}};
	void * myData = calloc(width * 4, height);
	CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
	CGContextRef myBitmapContext = CGBitmapContextCreate (myData,
	 width, height, 8,
	 width*4, space,
	 kCGBitmapByteOrder32Host |
	 kCGImageAlphaPremultipliedFirst);
	CGContextDrawImage(myBitmapContext, rect, myImageRef);
	CGContextRelease(myBitmapContext);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glGenTextures(1, texName);
	glBindTexture(GL_TEXTURE_RECTANGLE_ARB, *texName);
	glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
					GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexImage2D(GL_TEXTURE_2D,
                 0,
                 GL_RGBA8,
                 width, height,
                 0,
                 GL_BGRA_EXT,
                 GL_UNSIGNED_INT_8_8_8_8_REV,
                 myData);
	free(myData);
}

 

[Krevnik]

	CFURLRef url = CFURLCreateWithFileSystemPath(NULL, path, kCFURLPOSIXPathStyle, NO);
        //xCode troughs a warning about using NSString instead of CFString but since they are compatible it works anyway.

You can get rid of the warning by using an explicit type cast, like so:

	CFURLRef url = CFURLCreateWithFileSystemPath(NULL, (CFStringRef)path, kCFURLPOSIXPathStyle, NO);

Both types are pointers, so it will work. It will rid you of one more warning to worry about.

 

[lazydog]

Why would the dimensions need to be power of two? That seems like a huge disadvantage.

Yes, I guess that's why GL_TEXTURE_RECTANGLE_ARB etc was introduced!
b e n