How to change UIKit UIImage: drawInRect method for AppKIt NSImage: drawInRect method

Question

I port the iphone application to the Mac application, there I need to change the entire class associated with UIKit to AppKit. if you can help me really appreciate it. This is the best way to make lower parts.

Iphone App → using UIKit

UIGraphicsPushContext(ctx); [image drawInRect:rect]; UIGraphicsPopContext(); 

Mac Os - Using AppKit

 [NSGraphicsContext saveGraphicsState]; NSGraphicsContext * nscg = [NSGraphicsContext graphicsContextWithGraphicsPort:ctx flipped:YES]; [NSGraphicsContext setCurrentContext:nscg]; NSRect rect = NSMakeRect(offset.x * scale, offset.y * scale, scale * size.width, scale * size.height); [NSGraphicsContext restoreGraphicsState]; [image drawInRect:rect fromRect:NSMakeRect( 0, 0, [image size].width, [image size].height ) operation:NSCompositeClear fraction:1.0]; 

Answer 1

Documents and documents are your friends; they will explain a lot of things that you misuse here.

 [NSGraphicsContext saveGraphicsState]; NSGraphicsContext * nscg = [NSGraphicsContext graphicsContextWithGraphicsPort:ctx flipped:YES]; [NSGraphicsContext setCurrentContext:nscg]; 

You save the state of the graphics in the current context, and then immediately create a new context and set it as the current one.

 NSRect rect = NSMakeRect(offset.x * scale, offset.y * scale, scale * size.width, scale * size.height); 

That, apparently, is all you need. Creating a rectangle does not affect gstate, since it is not a drawing operation (a rectangle is just a set of numbers, you are not drawing a rectangle here).

In addition, you must use the current transformation matrix for the scale.

 [NSGraphicsContext restoreGraphicsState]; 

And then you are grestore in the context you created, and not the one you came across.

[Edit] Looking at this again after a year and a half, I think you misinterpreted the saveGraphicsState and restoreGraphicsState methods as the equivalent of UIGraphicsPushContext and UIGraphicsPopContext . They are not; saveGraphicsState and restoreGraphicsState click and select the graphical state of the current context. The current context is managed separately ( setCurrentContext: and does not have a push / pop API. [/ Edit]

I assume that you are using the CALayer drawInContext: method? If it is in NSView, then you already have the current context and do not (and should not) create it.

 [image drawInRect:rect fromRect:NSMakeRect( 0, 0, [image size].width, [image size].height ) operation:NSCompositeClear fraction:1.0]; 

The NSCompositeClear operation clears destination pixels, such as the Eraser tool in your favorite paint program. He does not draw an image. You want the NSCompositeSourceOver operation .