core-graphics

I have a semi-transparent view with a drop shadow. I mocked it up in photoshop, which doesn't draw the shadow under the object. Then I made it in xcode, but it obviously does draw the shadow underneath. I was wondering if there's a way to avoid this. In other words - have the shadow only appear outside of the shape? You probably want to set the rasterized property of the layer to YES, which will composite the shadow before other effects such as opacity are applied to the view. Note however that this has a big performance impact. There's a handy table of different shadow implementations and

I am looking to draw an image using Core Graphics.However I am able to draw the partial image i.e Horizontally & vertically. But instead of it I want to have it in a Diagonal Way.For more clarification, pls refer to below image : Real Image : Required Image Output: Below is the code using to fill the Layer with Color : CGContextRef contextRef = UIGraphicsGetCurrentContext(); CGContextMoveToPoint(contextRef, r.origin.x, r.origin.y ); CGContextAddLineToPoint(contextRef, r.origin.x , r.origin.y); CGContextAddLineToPoint(contextRef, r.origin.x + (r.size.width ), r.origin.y + (r.size.height));

I'm working on drawing code to erase part of an image. I'm not an expert on CoreGraphics and could use some help. This routine works fine, however, when moving fast, it loses touches (Not very smooth). Can this routine be modified to make CGContextClearRect smoother? Is there a better, faster way to do this? -(void)drawRect:(CGRect)rect { if (!myDrawing) { // touchpoints stored here myDrawing = [[NSMutableArray alloc] initWithCapacity:0]; } UIGraphicsBeginImageContext(frontImage.frame.size); [frontImage.image drawInRect:CGRectMake(0, 0, frontImage.frame.size.width, frontImage.frame.size.height

I want to draw an image using an additive blend mode. But I don't want to use OpenGL. I can't find anything to do this, maybe there's something in Quartz2D? Can anyone point me in the right direction? Cheers, Rich Krzysztof Zabłocki Sure there is enum CGBlendMode which you can use to specify blending operation. use method: CGContextSetBlendMode() or [image drawInRect:CGRectMake(0, 0, width, height) blendMode:mode alpha:1]; more at developer site: link text 来源： https://stackoverflow.com/questions/3908160/draw-an-image-in-additive-blend-mode-without-using-opengl

I am trying to create a perfect right half circle of 15 points radius with CGPathAddCurveToPoint, like this: CGPathMoveToPoint(path, NULL, 0, 0); CGPathAddCurveToPoint(path, NULL, 15, 0, 15, 30, 0, 30); It starts at the top middle of the circle. Then the first control point is set to the top right corner of the circle's bounding box. The second control point is set to the bottom right corner of the circle's bounding box. The circle ends at bottom middle of the bounding box. But when drawn, the circle has an egg-like shape. How can I make a perfect, flawless right semisphere starting at point 0