iOS整个APP实现灰色主题的示例代码

//image类别
- (UIImage *)getGrayImage {
    
  const int RED =1;
  const int GREEN =2;
  const int BLUE =3;
    
  UIImage *image = self;
    
  // Create image rectangle with current image width/height
  CGRect imageRect = CGRectMake(0,0, image.size.width* image.scale, image.size.height* image.scale);
    
  int width = imageRect.size.width;
  int height = imageRect.size.height;
    
  // the pixels will be painted to this array
  uint32_t *pixels = (uint32_t*) malloc(width * height *sizeof(uint32_t));
    
  // clear the pixels so any transparency is preserved
  memset(pixels,0, width * height *sizeof(uint32_t));
    
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    
  // create a context with RGBA pixels
  CGContextRef context = CGBitmapContextCreate(pixels, width, height,8, width *sizeof(uint32_t), colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedLast);
    
  // paint the bitmap to our context which will fill in the pixels array
  CGContextDrawImage(context,CGRectMake(0,0, width, height), [image CGImage]);
    
  for(int y = 0; y < height; y++) {
    for(int x = 0; x < width; x++) {
      uint8_t *rgbaPixel = (uint8_t*) &pixels[y * width + x];
        
      // convert to grayscale using recommended method: http://en.wikipedia.org/wiki/Grayscale#Converting_color_to_grayscale
      uint32_t gray = 0.3 * rgbaPixel[RED] +0.59 * rgbaPixel[GREEN] +0.11 * rgbaPixel[BLUE];
        
      // set the pixels to gray
      rgbaPixel[RED] = gray;
      rgbaPixel[GREEN] = gray;
      rgbaPixel[BLUE] = gray;
    }
  }
    
  // create a new CGImageRef from our context with the modified pixels
  CGImageRef imageRef = CGBitmapContextCreateImage(context);
    
  // we're done with the context, color space, and pixels
  CGContextRelease(context);
  CGColorSpaceRelease(colorSpace);
  free(pixels);
    
  // make a new UIImage to return
  UIImage *resultUIImage = [UIImage imageWithCGImage:imageRef scale:image.scale orientation:UIImageOrientationUp];
    
  // we're done with image now too
  CGImageRelease(imageRef);
    
  return resultUIImage;
  
}

    [self swizzleMethod:self orgSel:@selector(initWithRed:green:blue:alpha:) swizzSel:@selector(hdd_initWithRed:green:blue:alpha:)];
+ (UIColor *)hdd_colorWithRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue alpha:(CGFloat)a{
  CGFloat gray = red*0.299 + green*0.587 + blue*0.114;
  if ([CSDarkSiteManager isLocalCacheDarkSiteStatus]) {
    return [self hdd_colorWithRed:gray green:gray blue:gray alpha:a];
  }
  else {
    return [self hdd_colorWithRed:red green:green blue:blue alpha:a];
  }
}

+ (void)swizzHook {
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    Method originalMethod = class_getInstanceMethod([self class], @selector(initWithFrame:configuration:));
    Method swizzledMethod = class_getInstanceMethod([self class], @selector(lg_initWithFrame:configuration:));
    method_exchangeImplementations(originalMethod, swizzledMethod);
  });
}
- (instancetype)lg_initWithFrame:(CGRect)frame configuration:(WKWebViewConfiguration *)configuration {
  Class class = NSClassFromString(@"AIRWKWebView");
  if ([CSDarkSiteManager isLocalCacheDarkSiteStatus] && ![self isKindOfClass:class]) {
    NSString *jScript = @"var filter = '-webkit-filter:grayscale(100%);-moz-filter:grayscale(100%); -ms-filter:grayscale(100%); -o-filter:grayscale(100%) filter:grayscale(100%);';document.getElementsByTagName('html')[0].style.filter = 'grayscale(100%)';";
    // 注入
    WKUserScript *wkUScript = [[WKUserScript alloc] initWithSource:jScript injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES];
    [configuration.userContentController addUserScript:wkUScript];
    WKWebView *webView = [self lg_initWithFrame:frame configuration:configuration];
    return webView;
  }
  else {
    WKWebView *webView = [self lg_initWithFrame:frame configuration:configuration];
    return webView;
  }
  
}