Display NSImage on a CALayer - objective-c

Question

I've been trying to display a NSImage on a CALayer. Then I realised I need to convert it to a CGImage apparently, then display it...
I have this code which doesn't seem to be working
CALayer *layer = [CALayer layer];
NSImage *finderIcon = [[NSWorkspace sharedWorkspace] iconForFileType:NSFileTypeForHFSTypeCode(kFinderIcon)];
[finderIcon setSize:(NSSize){ 128.0f, 128.0f }];
CGImageSourceRef source;
source = CGImageSourceCreateWithData((CFDataRef)finderIcon, NULL);
CGImageRef finalIcon = CGImageSourceCreateImageAtIndex(source, 0, NULL);
layer.bounds = CGRectMake(128.0f, 128.0f, 4, 4);
layer.position = CGPointMake(128.0f, 128.0f);
layer.contents = finalIcon;
// Insert the layer into the root layer
[mainLayer addSublayer:layer];
Why? How can I get this to work?

Answer 1

From the comments: Actually, if you're on 10.6, you can also just set the CALayer's contents to an NSImage rather than a CGImageRef...
If you're on OS X 10.6 or later, take a look at NSImage's CGImageForProposedRect:context:hints: method.
If you're not, I've got this in a category on NSImage:
-(CGImageRef)CGImage
{
CGContextRef bitmapCtx = CGBitmapContextCreate(NULL/*data - pass NULL to let CG allocate the memory*/,
[self size].width,
[self size].height,
8 /*bitsPerComponent*/,
0 /*bytesPerRow - CG will calculate it for you if it's allocating the data. This might get padded out a bit for better alignment*/,
[[NSColorSpace genericRGBColorSpace] CGColorSpace],
kCGBitmapByteOrder32Host|kCGImageAlphaPremultipliedFirst);
[NSGraphicsContext saveGraphicsState];
[NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:bitmapCtx flipped:NO]];
[self drawInRect:NSMakeRect(0,0, [self size].width, [self size].height) fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
[NSGraphicsContext restoreGraphicsState];
CGImageRef cgImage = CGBitmapContextCreateImage(bitmapCtx);
CGContextRelease(bitmapCtx);
return (CGImageRef)[(id)cgImage autorelease];
}
I think I wrote this myself. But it's entirely possible that I ripped it off from somewhere else like Stack Overflow. It's an older personal project and I don't really remember.

Answer 2

Here's some code which may help you - I sure hope the formatting of this does not get all messed up like it appears is going to happen - all I can offer is that this works for me.
// -------------------------------------------------------------------------------------
- (void)awakeFromNib
{
// setup our main window 'contentWindow' to use layers
[[contentWindow contentView] setWantsLayer:YES]; // NSWindow*
// create a root layer to contain all of our layers
CALayer *root = [[contentWindow contentView] layer];
// use constraint layout to allow sublayers to center themselves
root.layoutManager = [CAConstraintLayoutManager layoutManager];
// create a new layer which will contain ALL our sublayers
// -------------------------------------------------------
mContainer = [CALayer layer];
mContainer.bounds = root.bounds;
mContainer.frame = root.frame;
mContainer.position = CGPointMake(root.bounds.size.width * 0.5,
root.bounds.size.height * 0.5);
// insert layer on the bottom of the stack so it is behind the controls
[root insertSublayer:mContainer atIndex:0];
// make it resize when its superlayer does
root.autoresizingMask = kCALayerWidthSizable | kCALayerHeightSizable;
// make it resize when its superlayer does
mContainer.autoresizingMask = kCALayerWidthSizable | kCALayerHeightSizable;
}
// -------------------------------------------------------------------------------------
- (void) loadMyImage:(NSString*) path
n:(NSInteger) num
x:(NSInteger) xpos
y:(NSInteger) ypos
h:(NSInteger) hgt
w:(NSInteger) wid
b:(NSString*) blendstr
{
#ifdef __DEBUG_LOGGING__
NSLog(#"loadMyImage - ENTER [%#] num[%d] x[%d] y[%d] h[%d] w[%d] b[%#]",
path, num, xpos, ypos, hgt, wid, blendstr);
#endif
NSInteger xoffset = ((wid / 2) + xpos); // use CORNER versus CENTER for location
NSInteger yoffset = ((hgt / 2) + ypos);
CIFilter* filter = nil;
CGRect cgrect = CGRectMake((CGFloat) xoffset, (CGFloat) yoffset,
(CGFloat) wid, (CGFloat) hgt);
if(nil != blendstr) // would be equivalent to #"CIMultiplyBlendMode" or similar
{
filter = [CIFilter filterWithName:blendstr];
}
// read image file via supplied path
NSImage* theimage = [[NSImage alloc] initWithContentsOfFile:path];
if(nil != theimage)
{
[self setMyImageLayer:[CALayer layer]]; // create layer
myImageLayer.frame = cgrect; // locate & size image
myImageLayer.compositingFilter = filter; // nil is OK if no filter
[myImageLayer setContents:(id) theimage]; // deposit image into layer
// add new layer into our main layer [see awakeFromNib above]
[mContainer insertSublayer:myImageLayer atIndex:0];
[theimage release];
}
else
{
NSLog(#"ERROR loadMyImage - no such image [%#]", path);
}
}

Answer 3

+ (CGImageRef) getCachedImage:(NSString *) imageName
{
NSGraphicsContext *context = [[NSGraphicsContext currentContext] graphicsPort];
NSImage *img = [NSImage imageNamed:imageName];
NSRect rect = NSMakeRect(0, 0, [img size].width, [img size].height);
return [img CGImageForProposedRect:&rect context:context hints:NULL];
}
+ (CGImageRef) getImage:(NSString *) imageName withExtension:(NSString *) extension
{
NSGraphicsContext *context = [[NSGraphicsContext currentContext] graphicsPort];
NSString* imagePath = [[NSBundle mainBundle] pathForResource:imageName ofType:extension];
NSImage* img = [[NSImage alloc] initWithContentsOfFile:imagePath];
NSRect rect = NSMakeRect(0, 0, [img size].width, [img size].height);
CGImageRef imgRef = [img CGImageForProposedRect:&rect context:context hints:NULL];
[img release];
return imgRef;
}
then you can set it:
yourLayer.contents = (id)[self getCachedImage:#"myImage.png"];
or
yourLayer.contents = (id)[self getImage:#"myImage" withExtension:#"png"];