Another IKImageView Question: copying a region

Question

I'm trying to use the select and copy feature of the IKImageView. If all you want to do is have an app with an image, select a portion and copy it to the clipboard, it's easy. You set the copy menu pick to the first responder's copy:(id) method and magically everything works.

However, if you want something more complicated, like you want to copy as part of some other operation, I can't seem to find the method to do this.

IKImageView doesn't seem to have a copy method, it doesn't seem to have a method that will even tell you the selected rectangle!

I have gone through Hillegass' book, so I understand how the clipboard works, just not how to get the portion of the image out of the view...

Now, I'm starting to think that I made a mistake in basing my project on IKImageView, but it's what Preview is built on (or so I've read), so I figured it had to be stable... and anyway, now it's too late, I'm too deep in this to start over...

So, other than not using IKImageView, any suggestions on how to copy the select region to the clipboard manually?

EDIT actually, I have found the copy(id) method, but when I call it, I get

 <Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 16 bits/pixel; 1-component color space; kCGImageAlphaPremultipliedLast; 2624 bytes/row.

Which obviously doesn't happen when I do a normal copy through the first-responder... I understand the error message, but I'm not sure where it's getting those parameters from...

Is there any way to trace through this and see how this is happening? A debugger won't help for obvious reasons, as well as the fact that I'm doing this in Mozilla, so a debugger isn't an option anyway...

EDIT 2 It occurs to me that the copy:(id) method I found may be copying the VIEW rather than copying a chunk of the image to the clipboard, which is what I need.

The reason I thought it was the clipboard copy is that in another project, where I'm copying from an IKImageView to the clipboard straight from the edit menu, it just sends a copy:(id) to the firstResponder, but I'm not actually sure what the firstresponder does with it...

EDIT 3 It appears that the CGBitmapContextCreate error is coming from [imageView image] which, oddly enough, IS a documented method.

It's possible that this is happening because I'm putting the image in there with a setImage:(id) method, passing it an NSImage*... Is there some other, more clever way of getting an NSImage into an IKImageView?

Answer 1

The -copy: method in IKImageView does what every other -copy: method does: it copies the current selection to the clipboard. It is, however, implemented as a private method in IKImageView for some reason.

You can just call it directly:

[imageView copy:nil];

This will copy whatever is currently selected to the clipboard.

I don't think there's a way to directly access the image content of the current selection in IKImageView using public methods, this is a good candidate for a bug report/feature request.

You can, however, use the private method -selectionRect to get a CGRect of the current selection and use that to extract the selected portion of the image:

//stop the compiler from complaining when we call a private method
@interface IKImageView (CompilerSTFU)
- (CGRect)selectionRect
@end

@implementation YourController
//imageView is an IBOutlet connected to your IKImageView
- (NSImage*)selectedImage
{
    //get the current selection
    CGRect selection = [imageView selectionRect];

    //get the portion of the image that the selection defines
    CGImageRef selectedImage = CGImageCreateWithImageInRect([imageView image],(CGRect)selection);

    //convert it to an NSBitmapImageRep
    NSBitmapImageRep* bitmap = [[[NSBitmapImageRep alloc] initWithCGImage:selectedImage] autorelease];
    CGImageRelease(selectedImage);

    //create an image from the bitmap data
    NSImage* image = [[[NSImage alloc] initWithData:[bitmap TIFFRepresentation]] autorelease];

    //in 10.6 you can skip converting to an NSBitmapImageRep by doing this:
    //NSImage* image = [[NSImage alloc] initWithCGImage:selectedImage size:NSZeroSize];     
    return image;
}
@end

Answer 2

Ok, so the copy: nil fails, and the [imageView image] fails, but it turns out that I have another copy of the NSImage from when I added it into the view in the first place, so I could that. Also, CGImageCreateWithImageInRect expects a CGImageRef not an NSImage*, so I had to do some conversions.

In addition, for some reason the selection rectangle is flipped, either it's bottom origined, and the image is top, or the other way around, so I had to flip it.

And for some reason, the compiler suddenly started complaining that NSRect isn't the same type as CGRect (Which implies that it suddenly went from 32 to 64 bit or something... not sure why...)

Anyway, here is my copy of selectedImage:

- (NSImage*)selectedImage
{
    //get the current selection
    CGRect selection = flipCGRect(imageView, [imageView selectionRect]);

    //get the portion of the image that the selection defines
    struct CGImage * full = [[doc currentImage] CGImageForProposedRect: NULL context: NULL hints: NULL];

    CGImageRef selectedImage = CGImageCreateWithImageInRect( full, selection);


    //convert it to an NSBitmapImageRep
    NSBitmapImageRep* bitmap = [[[NSBitmapImageRep alloc] initWithCGImage:selectedImage] autorelease];
    CGImageRelease(selectedImage);

//     //create an image from the bitmap data
    NSImage* image = [[[NSImage alloc] initWithData:[bitmap TIFFRepresentation]] autorelease];

//     //in 10.6 you can skip converting to an NSBitmapImageRep by doing this:
    //NSImage* image = [[NSImage alloc] initWithCGImage:selectedImage size:NSZeroSize];     
    return image;

}

I wrote flipCGRect, and [doc currentImage] returns an NSImage*...