AppKit Stretchable Image

gistfile1.m

@implementation NSImage (Stretchable)

- (void)drawStretchableInRect:(NSRect)rect edgeInsets:(NSEdgeInsets)insets operation:(NSCompositingOperation)op fraction:(CGFloat)delta {
  void (^makeAreas)(NSRect, NSRect *, NSRect *, NSRect *, NSRect *, NSRect *, NSRect *, NSRect *, NSRect *, NSRect *) = ^(NSRect srcRect, NSRect *tl, NSRect *tc, NSRect *tr, NSRect *ml, NSRect *mc, NSRect *mr, NSRect *bl, NSRect *bc, NSRect *br) {
    CGFloat w = NSWidth(srcRect);
    CGFloat h = NSHeight(srcRect);
    CGFloat cw = w - insets.left - insets.right;
    CGFloat ch = h - insets.top - insets.bottom;
    
    CGFloat x0 = NSMinX(srcRect);
    CGFloat x1 = x0 + insets.left;
    CGFloat x2 = NSMaxX(srcRect) - insets.right;
    
    CGFloat y0 = NSMinY(srcRect);
    CGFloat y1 = y0 + insets.bottom;
    CGFloat y2 = NSMaxY(srcRect) - insets.top;
    
    *tl = NSMakeRect(x0, y2, insets.left, insets.top);
    *tc = NSMakeRect(x1, y2, cw, insets.top);
    *tr = NSMakeRect(x2, y2, insets.right, insets.top);
    
    *ml = NSMakeRect(x0, y1, insets.left, ch);
    *mc = NSMakeRect(x1, y1, cw, ch);
    *mr = NSMakeRect(x2, y1, insets.right, ch);
    
    *bl = NSMakeRect(x0, y0, insets.left, insets.bottom);
    *bc = NSMakeRect(x1, y0, cw, insets.bottom);
    *br = NSMakeRect(x2, y0, insets.right, insets.bottom);
  };
  
  // Source rects
  NSRect srcRect = (NSRect){NSZeroPoint, self.size};
  NSRect srcTopL, srcTopC, srcTopR, srcMidL, srcMidC, srcMidR, srcBotL, srcBotC, srcBotR;
  makeAreas(srcRect, &srcTopL, &srcTopC, &srcTopR, &srcMidL, &srcMidC, &srcMidR, &srcBotL, &srcBotC, &srcBotR);
  
  // Destinations rects
  NSRect dstTopL, dstTopC, dstTopR, dstMidL, dstMidC, dstMidR, dstBotL, dstBotC, dstBotR;
  makeAreas(rect, &dstTopL, &dstTopC, &dstTopR, &dstMidL, &dstMidC, &dstMidR, &dstBotL, &dstBotC, &dstBotR);
  
  // Draw
  [self drawInRect:dstTopL fromRect:srcTopL operation:op fraction:delta];
  [self drawInRect:dstTopC fromRect:srcTopC operation:op fraction:delta];
  [self drawInRect:dstTopR fromRect:srcTopR operation:op fraction:delta];
  
  [self drawInRect:dstMidL fromRect:srcMidL operation:op fraction:delta];
  [self drawInRect:dstMidC fromRect:srcMidC operation:op fraction:delta];
  [self drawInRect:dstMidR fromRect:srcMidR operation:op fraction:delta];
  
  [self drawInRect:dstBotL fromRect:srcBotL operation:op fraction:delta];
  [self drawInRect:dstBotC fromRect:srcBotC operation:op fraction:delta];
  [self drawInRect:dstBotR fromRect:srcBotR operation:op fraction:delta];
}

@end