Mac OS截屏

从Snow Leopard系统开始，苹果直接提供了截取屏幕的API，使得之前通过读取分析屏幕信息进行截屏的方式大大简化。

 

#include "OpenGL/gl.h"

+ (NSImage *)capture
{
    CGImageRef imageRef = CGDisplayCreateImage(kCGDirectMainDisplay);
    NSImage *image = [[NSImage alloc]initWithCGImage:imageRef size:NSZeroSize];
    return image;
}

 

而在10.5之前，则类似于这样的代码：

 

+ (NSImage *)captureOld
{
    NSEnumerator * enumerator = [[NSScreen screens] objectEnumerator]; 
    id  obj = nil; 
    NSRect screenRect;      
    NSScreen * useThisScreen = [NSScreen mainScreen]; 
    //    NSRect rect = NSMakeRect(0, 0, 256, 256);
    NSRect rect = [useThisScreen frame];
    while (obj = [enumerator nextObject]) 
    { 
        screenRect = [obj frame]; 
        if ((rect.origin.x >= screenRect.origin.x) &&          
            (rect.origin.x <= screenRect.origin.x + screenRect.size.width) &&         
            
            (rect.origin.y >= screenRect.origin.y) &&  
            (rect.origin.y <= screenRect.origin.y + screenRect.size.height)) 
        { 
            useThisScreen = obj;           
        }       
    }      
    
    if (nil == useThisScreen) 
    { 
        NSLog(@"unable to find a valid screen");
        return nil;
    }       
    
    NSDictionary * descr = [useThisScreen deviceDescription]; 
    CGDirectDisplayID display = (CGDirectDisplayID)[[descr valueForKey:@"NSScreenNumber"] unsignedIntValue];              
    CGRect srcRect;
    srcRect.origin.x = rect.origin.x - [useThisScreen frame].origin.x;                 
    
    srcRect.origin.y = rect.origin.y - [useThisScreen frame].origin.y;                   
    
    srcRect.size.height = rect.size.height;         
    srcRect.size.width = rect.size.width; 
    
    CGContextRef bitmap;      
    CGColorSpaceRef cSpace = CGColorSpaceCreateDeviceRGB();                      
    
    CGLContextObj glContextObj; 
    CGLPixelFormatObj pixelFormatObj; 
    long numPixelFormats;    
    CGLPixelFormatAttribute attribs[] = 
    {          
        kCGLPFAFullScreen, 
        kCGLPFADisplayMask, 
        0,    // Display mask bit goes here 
        0 
    } ;    
    
    if ( display == kCGNullDirectDisplay ) 
        display = CGMainDisplayID(); 
    attribs[2] = CGDisplayIDToOpenGLDisplayMask(display); 
    
    // Build a full-screen GL context 
    CGLChoosePixelFormat( attribs, &pixelFormatObj, &numPixelFormats );               
    
    CGLCreateContext( pixelFormatObj, NULL, &glContextObj ) ;          
    
    CGLDestroyPixelFormat( pixelFormatObj ) ;                          
    
    CGLSetCurrentContext( glContextObj ) ; 
    CGLSetFullScreen( glContextObj ) ;                
    glReadBuffer(GL_FRONT); 
    
    void * data; 
    long bytewidth; 
    GLint width, height; 
    long bytes; 
    width = srcRect.size.width; 
    height = srcRect.size.height;           
    bytewidth = width * 4; // Assume 4 bytes/pixel for now 
    bytewidth = (bytewidth + 3) & ~3; // Align to 4 bytes 
    bytes = bytewidth * height; // width * height           
    
    // Build bitmap context _
    data = malloc(height * bytewidth); 
    bitmap = CGBitmapContextCreate(data, width, height, 8, bytewidth,            
                                   
                                   cSpace, kCGImageAlphaNoneSkipFirst);          
    
    CFRelease(cSpace); 
    
    // Read framebuffer into our bitmap        
    
    glFinish(); //Finish all OpenGL commands  
    glPixelStorei(GL_PACK_ALIGNMENT, 4); // Force 4-byte alignment               
    
    glPixelStorei(GL_PACK_ROW_LENGTH, 0); 
    glPixelStorei(GL_PACK_SKIP_ROWS, 0);
    glPixelStorei(GL_PACK_SKIP_PIXELS, 0);
    glReadPixels((GLint)srcRect.origin.x, (GLint)srcRect.origin.y, width, height, GL_BGRA, GL_UNSIGNED_BYTE,data);
    
    int i, j;
    unsigned char *tmpdata = (unsigned char *)data;
    char temp[4] = {0};
    for (i=0; i < height / 2; i ++) {
        for (j = 0; j < width; j ++) {
            memcpy(temp, tmpdata + bytewidth * i + j * 4, 4);
            memcpy(tmpdata + bytewidth * i + j * 4, tmpdata + bytewidth * (height - i - 1) + j * 4, 4);
            memcpy(tmpdata + bytewidth * (height - i - 1) + j * 4, temp, 4);
        }
    }
    
    CGImageRef newImage = CGBitmapContextCreateImage(bitmap);
    NSImage *img = [[NSImage alloc]initWithCGImage:newImage size:NSZeroSize];
    return img;
}