Opaque screenshot of render to texture

[kidproquo]

Hi,

I am doing some render to texture stuff using FBOs and Texture2D inside EAGLView (using the default OpenGL ES XCode project template).

The Texture2D object is initialized with a mist which is dynamically changed by rendering to an FBO. I setup the FBO this way:

		
		glGenFramebuffersOES(1, &mistFBO);
		glBindFramebufferOES(GL_FRAMEBUFFER_OES, mistFBO);
		glFramebufferTexture2DOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_TEXTURE_2D, self.mist.name, 0);
		GLuint status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);
		if (status != GL_FRAMEBUFFER_COMPLETE_OES)
		{
			// didn't work
		}

This mist is displayed over a background image.

Now, when my application quits, I want to save the mist state. I use this code to save:

- (void)applicationWillTerminate:(NSNotification *)notification 
{ 
           glBindFramebufferOES(GL_FRAMEBUFFER_OES, mistFBO);
	glViewport(0, 0, backingWidth, backingHeight);

	CGRect rect = [[UIScreen mainScreen] bounds];
	int width = rect.size.width;
	int height = rect.size.height;
		
	NSInteger myDataLength = width * height * 4;
	GLubyte *buffer = (GLubyte *) malloc(myDataLength);
	GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);

	//glPixelStorei(GL_PACK_ALIGNMENT, 1);
	glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
	for(int y = 0; y <height; y++) {
		for(int x = 0; x <width * 4; x++) {
			buffer2[((height - 1 - y) * width * 4 + x)] = buffer[(y * 4 * width + x)];
		}
	}
	free(buffer); // YOU CAN FREE THIS NOW
	
	CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, releaseData);
	int bitsPerComponent = 8;
	int bitsPerPixel = 32;
	int bytesPerRow = 4 * width;
	CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
	CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
	CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
	CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent); 
	
	CGColorSpaceRelease(colorSpaceRef); // YOU CAN RELEASE THIS NOW
	CGDataProviderRelease(provider); // YOU CAN RELEASE THIS NOW
	
	UIImage *image = [[UIImage alloc] initWithCGImage:imageRef]; // change this to manual alloc/init instead of autorelease
	CGImageRelease(imageRef); // YOU CAN RELEASE THIS NOW
	
           //Now lets  save the mist
	NSMutableData *data = [[NSMutableData alloc] init]; 
	NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] 
	
	NSData *mistData2 = UIImagePNGRepresentation(image); //just take a snapshot of the mist		
	[archiver encodeObject:mistData2 forKey:kMistKey];
		
	[archiver finishEncoding]; 
	[data writeToFile:[self dataFilePath] atomically:YES]; 								 initForWritingWithMutableData:data]; 
		
}

I load the archived mist on the next startup by:

           NSData *data = [[NSMutableData alloc] 
		initWithContentsOfFile:[self dataFilePath]]; 
	NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] 
											 initForReadingWithData:data]; 
	self.mistData = [unarchiver decodeObjectForKey:kMistKey]; 
			
	[unarchiver finishDecoding]; 
			
	UIImage *try = [UIImage imageWithData:self.mistData];
			
	self.mist = [[Texture2D alloc] initWithImage:try];

Now, when I load the archived mist on the next application launch, I see that the mist is opaque! That is, I am unable to see the background image through the mist, instead I just get a black background. If I disable mist display, the bg image does show.

If I ignore the archived mist and always initialize mist by this:

         self.mist = [[Texture2D alloc] initWithImage:[UIImage imageNamed:@"DefaultMist.png"]];

then it all works fine, but of course I do not have the mist state saved and retained.

Comments?

Regards,
Kid