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[Johanovski]

Hi there!

I'm working in an OpenGL application and when using .PNG images I've seen that OpenGL seems to draw a non-existing halo rounding the transparent part of the image... Why is this happening? Is there any way to avoid this halo? Here's the method I'm using to load an image:

- (id) initWithImage:(UIImage *)uiImage
{
	NSUInteger				width,
							height,
							i;
	CGContextRef			context = nil;
	void*					data = nil;;
	CGColorSpaceRef			colorSpace;
	void*					tempData;
	unsigned int*			inPixel32;
	unsigned short*			outPixel16;
	BOOL					hasAlpha;
	CGImageAlphaInfo		info;
	CGAffineTransform		transform;
	CGSize					imageSize;
	Texture2DPixelFormat    pixelFormat;
	CGImageRef				image;
	UIImageOrientation		orientation;
	BOOL					sizeToFit = NO;
	
	
	image = [uiImage CGImage];
	orientation = [uiImage imageOrientation]; 
	
	if(image == NULL) {
		[self release];
		NSLog(@"Image is Null");
		return nil;
	}
	

	info = CGImageGetAlphaInfo(image);
	hasAlpha = ((info == kCGImageAlphaPremultipliedLast) || (info == kCGImageAlphaPremultipliedFirst) || (info == kCGImageAlphaLast) || (info == kCGImageAlphaFirst) ? YES : NO);
	pixelFormat = kTexture2DPixelFormat_RGBA8888;	
	
	imageSize = CGSizeMake(CGImageGetWidth(image), CGImageGetHeight(image));
	transform = CGAffineTransformIdentity;

	width = imageSize.width;
	
	if((width != 1) && (width & (width - 1))) {
		i = 1;
		while((sizeToFit ? 2 * i : i) < width)
			i *= 2;
		width = i;
	}
	height = imageSize.height;
	if((height != 1) && (height & (height - 1))) {
		i = 1;
		while((sizeToFit ? 2 * i : i) < height)
			i *= 2;
		height = i;
	}
	while((width > kMaxTextureSize) || (height > kMaxTextureSize)) {
		width /= 2;
		height /= 2;
		transform = CGAffineTransformScale(transform, 0.5, 0.5);
		imageSize.width *= 0.5;
		imageSize.height *= 0.5;
	}
	
	switch(pixelFormat) {		
		case kTexture2DPixelFormat_RGBA8888:
			colorSpace = CGColorSpaceCreateDeviceRGB();
			data = malloc(height * width * 4);
			context = CGBitmapContextCreate(data, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
			CGColorSpaceRelease(colorSpace);
			break;
		case kTexture2DPixelFormat_RGB565:
			colorSpace = CGColorSpaceCreateDeviceRGB();
			data = malloc(height * width * 4);
			context = CGBitmapContextCreate(data, width, height, 8, 4 * width, colorSpace, kCGImageAlphaNoneSkipLast | kCGBitmapByteOrder32Big);
			CGColorSpaceRelease(colorSpace);
			break;
			
		case kTexture2DPixelFormat_A8:
			data = malloc(height * width);
			context = CGBitmapContextCreate(data, width, height, 8, width, NULL, kCGImageAlphaOnly);
			break;				
		default:
			[NSException raise:NSInternalInconsistencyException format:@"Invalid pixel format"];
	}
 

	CGContextClearRect(context, CGRectMake(0, 0, width, height));
	CGContextTranslateCTM(context, 0, height - imageSize.height);
	
	if(!CGAffineTransformIsIdentity(transform))
		CGContextConcatCTM(context, transform);
	CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), CGImageGetHeight(image)), image);
	//Convert "RRRRRRRRRGGGGGGGGBBBBBBBBAAAAAAAA" to "RRRRRGGGGGGBBBBB"
	if(pixelFormat == kTexture2DPixelFormat_RGB565) {
		tempData = malloc(height * width * 2);
		inPixel32 = (unsigned int*)data;
		outPixel16 = (unsigned short*)tempData;
		for(i = 0; i < width * height; ++i, ++inPixel32)
			*outPixel16++ = ((((*inPixel32 >> 0) & 0xFF) >> 3) << 11) | ((((*inPixel32 >> 8) & 0xFF) >> 2) << 5) | ((((*inPixel32 >> 16) & 0xFF) >> 3) << 0);
		free(data);
		data = tempData;
		
	}
	self = [self initWithData:data pixelFormat:pixelFormat pixelsWide:width pixelsHigh:height contentSize:imageSize];
	
	CGContextRelease(context);
	free(data);
	
	return self;
}

- (id) initWithData:(const void*)data pixelFormat:(Texture2DPixelFormat)pixelFormat pixelsWide:(NSUInteger)width pixelsHigh:(NSUInteger)height contentSize:(CGSize)size
{
	GLint					saveName;
	if((self = [super init])) {
		glGenTextures(1, &_name);
		glGetIntegerv(GL_TEXTURE_BINDING_2D, &saveName);
		glBindTexture(GL_TEXTURE_2D, _name);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
		switch(pixelFormat) {
			
			case kTexture2DPixelFormat_RGBA8888:
				glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
				break;
			case kTexture2DPixelFormat_RGB565:
				glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, data);
				break;
			case kTexture2DPixelFormat_A8:
				glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, width, height, 0, GL_ALPHA, GL_UNSIGNED_BYTE, data);
				break;
			default:
				[NSException raise:NSInternalInconsistencyException format:@""];
			
		}
		glBindTexture(GL_TEXTURE_2D, saveName);
	
		_size = size;
		_width = width;
		_height = height;
		_format = pixelFormat;
		_maxS = size.width / (float)width;
		_maxT = size.height / (float)height;
	}					
	return self;
}

Anyone know anything about this?

Thanks in advance!