如何使用 Cocoa 和 CGDisplayCreateImageForRect 在 Mac OS X 中截取区域截图？

Posted 2023-02-16

【中文标题】如何使用 Cocoa 和 CGDisplayCreateImageForRect 在 Mac OS X 中截取区域截图？

【英文标题】：How to take region screenshot in Mac OS X using Cocoa and CGDisplayCreateImageForRect?

【发布时间】：2012-10-10 15:53:29

【问题描述】：

我找到了如何制作全尺寸截图How to take screenshot in Mac OS X using Cocoa or C++，但是我如何制作区域截图？

【问题讨论】：

先阅读documentation for CGDisplayCreateImageForRect，然后问一个更具体的问题...

我知道。 CGDisplayCreateImageForRect如何获取鼠标坐标？

【参考方案1】：

抱歉，格式很丑。第二个函数正是你想要的。

//  this is a cute function for creating CGImageRef from NSImage.
//  I found it somewhere on SO but I do not remember the link, I am sorry..
CGImageRef CGImageCreateWithNSImage(NSImage *image) 
    NSSize imageSize = [image size];

    CGContextRef bitmapContext = CGBitmapContextCreate(NULL, imageSize.width, imageSize.height, 8, 0, [[NSColorSpace genericRGBColorSpace] CGColorSpace], kCGBitmapByteOrder32Host|kCGImageAlphaPremultipliedFirst);

    [NSGraphicsContext saveGraphicsState];
    [NSGraphicsContext setCurrentContext:[NSGraphicsContext graphicsContextWithGraphicsPort:bitmapContext flipped:NO]];
    [image drawInRect:NSMakeRect(0, 0, imageSize.width, imageSize.height) fromRect:NSZeroRect operation:NSCompositeCopy fraction:1.0];
    [NSGraphicsContext restoreGraphicsState];

    CGImageRef cgImage = CGBitmapContextCreateImage(bitmapContext);
    CGContextRelease(bitmapContext);
    return cgImage;


NSImage* NSImageFromScreenWithRect(CGRect rect)

    //  copy screenshot to clipboard, works on OS X only..
    system("screencapture -c -x");

    //  get NSImage from clipboard..
    NSImage *imageFromClipboard=[[NSImage alloc]initWithPasteboard:[NSPasteboard generalPasteboard]];

    //  get CGImageRef from NSImage for further cutting..
    CGImageRef screenShotImage=CGImageCreateWithNSImage(imageFromClipboard);

    //  cut desired subimage from fullscreen screenshot..
    CGImageRef screenShotCenter=CGImageCreateWithImageInRect(screenShotImage,rect);

    //  create NSImage from CGImageRef..
    NSImage *resultImage=[[NSImage alloc]initWithCGImage:screenShotCenter size:rect.size];

    //  release CGImageRefs cause ARC has no effect on them..
    CGImageRelease(screenShotCenter);
    CGImageRelease(screenShotImage);

    return resultImage;