+(UIImage *)fullScreenshots{

    UIWindow *screenWindow = [[UIApplication sharedApplication] keyWindow];

    //    UIGraphicsBeginImageContext(screenWindow.frame.size);//全屏截图，包括window

    UIGraphicsBeginImageContextWithOptions(screenWindow.frame.size,YES,0.0);

    [screenWindow.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return viewImage;

}

+ (UIImage*)screenShot

{

    // Create a graphics context with the target size

    // On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration

    // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext

    CGSize imageSize = [[UIScreen mainScreen] bounds].size;

    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);

    CGContextRef context = UIGraphicsGetCurrentContext();

    // Iterate over every window from back to front

    for (UIWindow *window in [[UIApplication sharedApplication] windows])

    {

        if ( [window screen] == [UIScreen mainScreen])

        {

            // -renderInContext: renders in the coordinate space of the layer,

            // so we must first apply the layer's geometry to the graphics context

            CGContextSaveGState(context);

            // Center the context around the window's anchor point

            CGContextTranslateCTM(context, [window center].x, [window center].y);

            // Apply the window's transform about the anchor point

            CGContextConcatCTM(context, [window transform]);

            // Offset by the portion of the bounds left of and above the anchor point

            CGContextTranslateCTM(context,

                                  -[window bounds].size.width * [[window layer] anchorPoint].x,

                                  -[window bounds].size.height * [[window layer] anchorPoint].y);

            // Render the layer hierarchy to the current context

            [[window layer] renderInContext:context];

            // Restore the context

            CGContextRestoreGState(context);

        }

    }

    // Retrieve the screenshot image

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;

}　

- (UIImage*) takePicture {

    int s = 1;

    UIScreen* screen = [UIScreen mainScreen];

    if ([screen respondsToSelector:@selector(scale)]) {

        s = (int) [screen scale];

    }

    GLint viewport[4];

    glGetIntegerv(GL_VIEWPORT, viewport);

    int width = viewport[2];

    int height = viewport[3];

    int myDataLength = width * height * 4;

    GLubyte *buffer = (GLubyte *) malloc(myDataLength);

    GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);

    glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);

    for(int y1 = 0; y1 < height; y1++) {

        for(int x1 = 0; x1 <width * 4; x1++) {

            buffer2[(height - 1 - y1) * width * 4 + x1] = buffer[y1 * 4 * width + x1];

        }

    }

    free(buffer);

    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);

    int bitsPerComponent = 8;

    int bitsPerPixel = 32;

    int bytesPerRow = 4 * width;

    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();

    CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;

    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

    CGImageRef imageRef = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);

    CGColorSpaceRelease(colorSpaceRef);

    CGDataProviderRelease(provider);

    UIImage *image = [ UIImage imageWithCGImage:imageRef scale:s orientation:UIImageOrientationUp ];

    return image;

}

+ (float)colorAtPixel:(CGPoint)point  image:(UIImage *)image

{

    // Cancel if point is outside image coordinates

    if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), point)) {

        return 1000.0;

    }

    NSInteger pointX = trunc(point.x);

    NSInteger pointY = trunc(point.y);

    CGImageRef cgImage = image.CGImage;

    NSUInteger width = image.size.width;

    NSUInteger height = image.size.height;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    int bytesPerPixel = 4;

    int bytesPerRow = bytesPerPixel * 1;

    NSUInteger bitsPerComponent = 8;

    unsigned char pixelData[4] = { 0, 0, 0, 0 };

    CGContextRef context = CGBitmapContextCreate(pixelData,1,1,

                                                 bitsPerComponent,

                                                 bytesPerRow,

                                                 colorSpace,

                                                 kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);

    CGColorSpaceRelease(colorSpace);

    CGContextSetBlendMode(context, kCGBlendModeCopy);

    // Draw the pixel we are interested in onto the bitmap context

    CGContextTranslateCTM(context, -pointX, pointY - (CGFloat)height);

    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage);

    CGContextRelease(context);

    // Convert color values [0..255] to floats [0.0..1.0]

    CGFloat red = (CGFloat)pixelData[0] / 1.0f;

    CGFloat green = (CGFloat)pixelData[1] / 1.0;

    CGFloat blue = (CGFloat)pixelData[2] / 1.0f;

    //    CGFloat alpha = (CGFloat)pixelData[3] / 255.0f;

    //    NSLog(@" colors: RGB  %f %f %f  %f", red, green, blue, alpha);

    return red + green + blue;

}