1.          UIGraphicsBeginImageContextWithOptions(pageView.page.bounds.size, YES, zoomScale);          [pageView.page.layer renderInContext:UIGraphicsGetCurrentContext()];          UIImage *uiImage = UIGraphicsGetImageFromCurrentImageContext();          UIGraphicsEndImageContext();  2.  - (UIImage *) glToUIImage {            DWScrollView *pageView = [self getActivePageView];         pageView.page.backgroundColor = [UIColor clearColor];    //  self.backgroundColor=[UIColor clearColor];      NSInteger myDataLength = 320 * 308 * 4;            // allocate array and read pixels into it.      GLubyte *buffer = (GLubyte *) malloc(myDataLength);      glReadPixels(0, 0, 320, 308, GL_RGBA, GL_UNSIGNED_BYTE, buffer);            // gl renders "upside down" so swap top to bottom into new array.      // there's gotta be a better way, but this works.      GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);            for(int y = 0; y <308; y++)      {          for(int x = 0; x <320 * 4; x++)          {              if(buffer[y* 4 * 320 + x]==0)                  buffer2[(307 - y) * 320 * 4 + x]=1;              else                  buffer2[(307 - y) * 320 * 4 + x] = buffer[y* 4 * 320 + x];          }      }            // make data provider with data.      CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);            // prep the ingredients      int bitsPerComponent = 8;      int bitsPerPixel = 32;      int bytesPerRow = 4 * 320;      CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();      CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;      CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;            // make the cgimage      CGImageRef imageRef = CGImageCreate(320, 308, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);            // then make the uiimage from that      UIImage *myImage = [UIImage imageWithCGImage:imageRef];      UIImageWriteToSavedPhotosAlbum(myImage, nil, nil, nil);      return myImage;  }    3.  // get screen  - (void)grabScreen {      unsigned char buffer[320*480*4];      glReadPixels(0,0,320,480,GL_RGBA,GL_UNSIGNED_BYTE,&buffer);            CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, &buffer, 320*480*4, NULL);      CGImageRef iref = CGImageCreate(320,480,8,32,320*4,CGColorSpaceCreateDeviceRGB(),kCGBitmapByteOrderDefault,ref,NULL,true,kCGRenderingIntentDefault);      CGFloat width = CGImageGetWidth(iref);      CGFloat height = CGImageGetHeight(iref);      size_t length = width*height*4;      uint32_t *pixels = (uint32_t *)malloc(length);      CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, 320*4, CGImageGetColorSpace(iref), kCGImageAlphaLast | kCGBitmapByteOrder32Big);      CGContextTranslateCTM(context, 0.0, height);      CGContextScaleCTM(context, 1.0, -1.0);      CGContextDrawImage(context, CGRectMake(0.0, 0.0, width, height), iref);      CGImageRef outputRef = CGBitmapContextCreateImage(context);      UIImage *outputImage = [UIImage imageWithCGImage:outputRef];            UIImageWriteToSavedPhotosAlbum(outputImage, nil, nil, nil);             CGContextRelease(context);      CGImageRelease(iref);      CGDataProviderRelease(ref);  }   4.  CGImageRef UIGetScreenImage();  void SaveScreenImage(NSString *path)  {      NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];      CGImageRef cgImage = UIGetScreenImage();          void *imageBytes = NULL;          if (cgImage == NULL) {                  CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();                  imageBytes = malloc(320 * 480 * 4);                  CGContextRef context = CGBitmapContextCreate(imageBytes, 320, 480, 8, 320 * 4, colorspace, kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big);                  CGColorSpaceRelease(colorspace);                  for (UIWindow *window in [[UIApplication sharedApplication] windows]) {                          CGRect bounds = [window bounds];                          CALayer *layer = [window layer];                          CGContextSaveGState(context);                          if ([layer contentsAreFlipped]) {                                  CGContextTranslateCTM(context, 0.0f, bounds.size.height);                                  CGContextScaleCTM(context, 1.0f, -1.0f);                          }                          [layer renderInContext:(CGContextRef)context];                          CGContextRestoreGState(context);                  }                  cgImage = CGBitmapContextCreateImage(context);                  CGContextRelease(context);          }      NSData *pngData = UIImagePNGRepresentation([UIImage imageWithCGImage:cgImage]);      CGImageRelease(cgImage);          if (imageBytes)                  free(imageBytes);      [pngData writeToFile:path atomically:YES];      [pool release];  }    5.    + (UIImage *)imageWithScreenContents  {       CGImageRef cgScreen = UIGetScreenImage();       if (cgScreen) {           UIImage *result = [UIImage imageWithCGImage:cgScreen];           CGImageRelease(cgScreen);           return result;       }       return nil;  }       在程序中如何把两张图片合成为一张图片     - (UIImage *)addImage:(UIImage *)image1 toImage:(UIImage *)image2 {        UIGraphicsBeginImageContext(image1.size);          // Draw image1        [image1 drawInRect:CGRectMake(0, 0, image1.size.width, image1.size.height)];          // Draw image2        [image2 drawInRect:CGRectMake(0, 0, image2.size.width, image2.size.height)];          UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();          UIGraphicsEndImageContext();          return resultingImage;    }