Question

I want to set a custom mouse cursor for my app and would like to programmatically change the default cursor’s color to a custom color by replacing the white border with the custom color. The problem is that I don’t even know where to start to programmatically edit images in Cocoa, so any help is appreciated!

Answer 1

My final code. This takes the standard IBeam cursor (that one when you hover over a textview) and stores the colored cursor in the coloredIBeamCursor pointer.

- (void)setPointerColor:(NSColor *)newColor {
    // create the new cursor image
    [[NSGraphicsContext currentContext] CIContext];
    // create the layer with the same color as the text
    CIFilter *backgroundGenerator=[CIFilter filterWithName:@"CIConstantColorGenerator"];
    CIColor *color=[[[CIColor alloc] initWithColor:newColor] autorelease];
    [backgroundGenerator setValue:color forKey:@"inputColor"];
    CIImage *backgroundImage=[backgroundGenerator valueForKey:@"outputImage"];
    // create the cursor image
    CIImage *cursor=[CIImage imageWithData:[[[NSCursor IBeamCursor] image] TIFFRepresentation]];
    CIFilter *filter=[CIFilter filterWithName:@"CIColorInvert"];
    [filter setValue:cursor forKey:@"inputImage"];
    CIImage *outputImage=[filter valueForKey:@"outputImage"];
    // apply a multiply filter
    filter=[CIFilter filterWithName:@"CIMultiplyCompositing"];
    [filter setValue:backgroundImage forKey:@"inputImage"];
    [filter setValue:outputImage forKey:@"inputBackgroundImage"];
    outputImage=[filter valueForKey:@"outputImage"];
    // get the NSImage from the CIImage
    NSCIImageRep *rep=[NSCIImageRep imageRepWithCIImage:outputImage];
    NSImage *newImage=[[[NSImage alloc] initWithSize:[outputImage extent].size] autorelease];
    [newImage addRepresentation:rep];
    // remove the old cursor (if any)
    if (coloredIBeamCursor!=nil) {
        [self removeCursorRect:[self visibleRect] cursor:coloredIBeamCursor];
        [coloredIBeamCursor release];
    }
    // set the new cursor
    NSCursor *coloredIBeamCursor=[[NSCursor alloc] initWithImage:newImage hotSpot:[[NSCursor IBeamCursor] hotSpot]];
    [self resetCursorRects];
}