CocoaDev

A CIImage object represents an immutable image in CoreImage.

It is tempting to use NSBitmapImageRep in the following manner to build a CIImage.

NSBitmapImageRep * bitmap = … //bitmap want to convert CIImage *initialCIImage = [[CIImage alloc] initWithBitmapImageRep:bitmap];

Be warned, this seems to be unreliable. In particular it seems that the internal bytesPerRow is not a multiple of 16 and then in some circumstances artifacts like skewing occur (the docs only recommend 16 but don’t say it is compulsary - possible Apple bug?)

I’ve been using the following code with success to draw into a bitmap for use in CIImage – RbrtPntn

NSRect rect = … the (0,0,width,height) bounds of the final image

// Build an offscreen CGContext int bytesPerRow = rect.size.width*4; //bytes per row - one byte each for argb bytesPerRow += (16 - bytesPerRow%16)%16; // ensure it is a multiple of 16 size_t byteSize = bytesPerRow * rect.size.height; void * bitmapData = malloc(byteSize); //bzero(bitmapData, byteSize); //only necessary if don’t draw the entire image

CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB); CGContextRef cg = CGBitmapContextCreate(bitmapData, rect.size.width, rect.size.height, 8, // bits per component bytesPerRow, colorSpace, kCGImageAlphaPremultipliedFirst); //later want kCIFormatARGB8 in CIImage

// Ensure the y-axis is flipped CGContextTranslateCTM(cg, 0, rect.size.height); CGContextScaleCTM(cg, 1.0, -1.0 ); CGContextSetPatternPhase(cg, CGSizeMake(0,rect.size.height));

// Draw into the offscreen CGContext [NSGraphicsContext saveGraphicsState]; NSGraphicsContext * nscg = [NSGraphicsContext graphicsContextWithGraphicsPort:cg flipped:NO]; [NSGraphicsContext setCurrentContext:nscg];

// Here is where you want to do all of your drawing...
[[NSColor blueColor] set];
[NSBezierPath fillRect:rect];
// etc, etc...

[NSGraphicsContext restoreGraphicsState]; CGContextRelease(cg);

// Extract the CIImage from the raw bitmap data that was used in the offscreen CGContext CIImage * coreimage = [[CIImage alloc] initWithBitmapData:[NSData dataWithBytesNoCopy:bitmapData length:byteSize] bytesPerRow:bytesPerRow size:CGSizeMake(rect.size.width, rect.size.height) format:kCIFormatARGB8 colorSpace:colorSpace];

// Housekeeping CGColorSpaceRelease(colorSpace);

return coreimage;

I’m having a lot of trouble making a simple NSImage black and white using CoreImage (I’m new to it), and turning the NSImage to a CIImage is the issue. Here is my drawRect code segment:

CIContext *bwimage;
CIImage *resimage, *ciresult;
CIFilter *bwfilter; ...
if (isBlackAndWhite) {
	bwimage = [[NSGraphicsContext currentContext] CIContext];
	bwfilter = [CIFilter filterWithName:@"CIColorMonochrome"];
	[bwfilter setDefaults];
	ciresult = [CIImage imageWithData:self image] [[TIFFRepresentation]];
	[bwfilter setValue:ciresult forKey:@"inputImage"];
	[bwfilter setValue:[CIColor colorWithRed:0 green:0 blue:0] forKey:@"inputColor"];
	resimage = [bwfilter valueForKey:@"outputImage"];
	[resimage drawAtPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1];
}

This does nothing.

If I use the above function code:

// code by Robert Pointon

• (CIImage *)coreImageResult { // CODE BY PIETRO GAGLIARDI MODIFYING ORIGINAL NSRect rect;

  rect.origin = NSZeroPoint; rect.size = self image] size]; // END CODE // Build an offscreen [[CGContext int bytesPerRow = rect.size.width*4; //bytes per row - one byte each for argb bytesPerRow += (16 - bytesPerRow%16)%16; // ensure it is a multiple of 16 size_t byteSize = bytesPerRow * rect.size.height; void * bitmapData = malloc(byteSize); //bzero(bitmapData, byteSize); //only necessary if don’t draw the entire image

  CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB); CGContextRef cg = CGBitmapContextCreate(bitmapData, rect.size.width, rect.size.height, 8, // bits per component bytesPerRow, colorSpace, kCGImageAlphaPremultipliedFirst); //later want kCIFormatARGB8 in CIImage

  // Ensure the y-axis is flipped CGContextTranslateCTM(cg, 0, rect.size.height); CGContextScaleCTM(cg, 1.0, -1.0 ); CGContextSetPatternPhase(cg, CGSizeMake(0,rect.size.height));

  // Draw into the offscreen CGContext [NSGraphicsContext saveGraphicsState]; NSGraphicsContext * nscg = [NSGraphicsContext graphicsContextWithGraphicsPort:cg flipped:NO]; [NSGraphicsContext setCurrentContext:nscg];

    // Here is where you want to do all of your drawing...
    // BEGIN CODE BY PIETRO GAGLIARDI, REPLACING OLD CODE
    self image] drawInRect:rect fromRect:[[NSZeroRect operation:NSCompositeSourceOver fraction:1];
    // END CODE
    // etc, etc...
  

  [NSGraphicsContext restoreGraphicsState]; CGContextRelease(cg);

  // Extract the CIImage from the raw bitmap data that was used in the offscreen CGContext CIImage * coreimage = [[CIImage alloc] initWithBitmapData:[NSData dataWithBytesNoCopy:bitmapData length:byteSize] bytesPerRow:bytesPerRow size:CGSizeMake(rect.size.width, rect.size.height) format:kCIFormatARGB8 colorSpace:colorSpace];

  // Housekeeping CGColorSpaceRelease(colorSpace);

  return coreimage; }

and do this:

	ciresult = [self coreImageResult];

This also does nothing. What am I doing wrong? - PietroGagliardi