Drawing Image with CGImage?

Question

I have my CGImageRef and i want to display it trough my NSView. But this code doesn't seem to work, i already have an CGImageRef from source path. Here's my code :

- (void)drawRect:(NSRect)rect {

NSString *   thePath = [[NSBundle mainBundle] pathForResource: @"blue_pict"
                                                    ofType: @"jpg"];
NSLog(@"the path : %@", thePath);

CGImageRef myDrawnImage = [self createCGImageRefFromFile:thePath];

NSLog(@"get the context");
CGContextRef context = (CGContextRef)[[NSGraphicsContext currentContext]     graphicsPort];
if (context==nil) {
    NSLog(@"context failed");
    return;
}

//get the bitmap context
CGContextRef myContextRef = CreateARGBBitmapContext(myDrawnImage);

//set the rectangle
NSLog(@"get the size for imageRect");
size_t w = CGImageGetWidth(myDrawnImage);
size_t h = CGImageGetHeight(myDrawnImage);
CGRect imageRect = {{0,0}, {w,h}};
NSLog(@"W : %d", w);

myDrawnImage = CGBitmapContextCreateImage(myContextRef);

NSLog(@"now draw it");
CGContextDrawImage(context, imageRect, myDrawnImage);

char *bitmapData = CGBitmapContextGetData(myContextRef);

NSLog(@"and release it");
CGContextRelease(myContextRef);
if (bitmapData) free(bitmapData);
CGImageRelease(myDrawnImage);

}

Is anything wrong with the codes?

• Thanks & Regard -

Answer 1

Yes, you don't actually draw the image. All you need to do is use CGContextDrawImage instead of creating an empty bitmap context.

Answer 2

CGImageRef myDrawnImage = [self createCGImageRefFromFile:thePath];

Now you have your image.

CGContextRef context = (CGContextRef)[[NSGraphicsContext currentContext]     graphicsPort];

Now you have your view's context. You have everything you need to draw the image.

CGContextRef myContextRef = CreateARGBBitmapContext(myDrawnImage);

Wait, what?

myDrawnImage = CGBitmapContextCreateImage(myContextRef);

O…kay… now you have captured the contents of a context that nothing has drawn in, forgetting about (and leaking) your loaded image by replacing it with a blank image.

CGContextDrawImage(context, imageRect, myDrawnImage);

You draw the blank image.

Cut out the creation of a bitmap context and the creation of an image of the contents of that context, and just draw the image you loaded into the context for your view.

Or use NSImage. That would be a two-liner.