NSImage transparency
I am trying to set a custom drag and drop icon for use in an NSTableView. Everything seems to work, but I ran into a problem due to my inexperience with Quartz.
- (NSImage *)dragImageForRowsWithIndexes:(NSIndexSet *)dragRows tableColumns:(NSArray *)tableColumns event:(NSEvent *)dragEvent offset:(NSPointPointer)dragImageOffset
{
NSImage *dragImage = [NSImage imageNamed:@"icon.png"];
NSString *count = [NSString stringWithFormat:@"%d", [dragRows count]];
[dragImage lockFocus];
[dragImage compositeToPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:0.5];
[count drawAtPoint:NSZeroPoint withAttributes:nil];
[dragImage unlockFocus];
return dragImage;
}
Basically I want to make my icon.png file with 50% opacity along with an NSString that shows the number of lines being dragged. The problem I see is that my NSString is rendering at low opacity, but not my icon.
+1
source to share
1 answer
The problem is you are drawing your icon on top of yourself. What you probably want is something like this:
- (NSImage *)dragImageForRowsWithIndexes:(NSIndexSet *)dragRows tableColumns:(NSArray *)tableColumns event:(NSEvent *)dragEvent offset:(NSPointPointer)dragImageOffset
{
NSImage *icon = [NSImage imageNamed:@"icon.png"];
NSString *count = [NSString stringWithFormat:@"%lu", [dragRows count]];
NSImage *dragImage = [[[NSImage alloc] initWithSize:[icon size]] autorelease];
[dragImage lockFocus];
[icon drawAtPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:0.5];
[count drawAtPoint:NSZeroPoint withAttributes:nil];
[dragImage unlockFocus];
return dragImage;
}
+3
source to share