获取当前显示屏幕某一点的颜色

1、获取当前屏幕的截图

-(UIImage *)fullScreenshots{UIWindow *screenWindow = [[UIApplication sharedApplication] keyWindow];UIGraphicsBeginImageContext(screenWindow.frame.size);//全屏截图，包括window[screenWindow.layer renderInContext:UIGraphicsGetCurrentContext()];UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();return viewImage;}

2、通过图片获取点颜色

- (UIColor*) getPixelColorAtLocation:(CGPoint)point withImage:(UIImage*) image {UIColor* color = nil;CGImageRef inImage = image.CGImage;// Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, BlueCGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];if (cgctx == NULL) { return nil;  }size_t w = CGImageGetWidth(inImage);size_t h = CGImageGetHeight(inImage);CGRect rect = {{0,0},{w,h}};// Draw the image to the bitmap context. Once we draw, the memory// allocated for the context for rendering will then contain the// raw image data in the specified color space.CGContextDrawImage(cgctx, rect, inImage);// Now we can get a pointer to the image data associated with the bitmap// context.unsigned char* data = CGBitmapContextGetData (cgctx);if (data != NULL) {//offset locates the pixel in the data from x,y.//4 for 4 bytes of data per pixel, w is width of one row of data.@try {int offset = 4*((w*round(point.y))+round(point.x));NSLog(@"offset: %d", offset);int alpha =  data[offset];int red = data[offset+1];int green = data[offset+2];int blue = data[offset+3];NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)];}@catch (NSException * e) {NSLog(@"%@",[e reason]);}@finally {}}return color;
}
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {CGContextRef    context = NULL;CGColorSpaceRef colorSpace;void *          bitmapData;int             bitmapByteCount;int             bitmapBytesPerRow;// Get image width, height. We'll use the entire image.size_t pixelsWide = CGImageGetWidth(inImage);size_t pixelsHigh = CGImageGetHeight(inImage);// Declare the number of bytes per row. Each pixel in the bitmap in this// example is represented by 4 bytes; 8 bits each of red, green, blue, and// alpha.bitmapBytesPerRow   = (pixelsWide * 4);bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh);// Use the generic RGB color space.colorSpace = CGColorSpaceCreateDeviceRGB();if (colorSpace == NULL){fprintf(stderr, "Error allocating color spacen");return NULL;}// Allocate memory for image data. This is the destination in memory// where any drawing to the bitmap context will be rendered.bitmapData = malloc( bitmapByteCount );if (bitmapData == NULL){fprintf (stderr, "Memory not allocated!");CGColorSpaceRelease( colorSpace );return NULL;}// Create the bitmap context. We want pre-multiplied ARGB, 8-bits// per component. Regardless of what the source image format is// (CMYK, Grayscale, and so on) it will be converted over to the format// specified here by CGBitmapContextCreate.context = CGBitmapContextCreate (bitmapData,pixelsWide,pixelsHigh,8,      // bits per componentbitmapBytesPerRow,colorSpace,kCGImageAlphaPremultipliedFirst);if (context == NULL){free (bitmapData);fprintf (stderr, "Context not created!");}// Make sure and release colorspace before returningCGColorSpaceRelease( colorSpace );return context;
}

3、使用方法

- (void)webViewDidFinishLoad:(UIWebView *)webView {    if (_backView) {[self performSelector:@selector(changeColor) withObject:nil afterDelay:.5];}
}
- (void) changeColor {UIColor* color = [self getPixelColorAtLocation:CGPointMake(4, 22) withImage:[self fullScreenshots]];if (color && !CGColorEqualToColor(color.CGColor, _backView.backgroundColor.CGColor)) {_backView.backgroundColor = color;}
}

在url加载完成后，根据webview的navigationbar颜色确定状态栏背景颜色，保持一致风格

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获取当前显示屏幕某一点的颜色

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