iOS整个APP实现灰色主题的示例代码

灰色主题

背景

在一些哀悼日，清明节的时候app会实现一些灰色主题功能，部分app需求是tab首页实现灰色模式就可以，但一些需求是直接整个app都变为灰色模。

• 普通UI界面
• web页面
• xib界面
• attributeText加载的htmlString页面
• attachment挂件页面

实现方式

基本的实现方式1，普通页面用hook颜色方式2.web页面用注入灰色js实现方式

图片变灰

重新绘制图片变为灰色代码实现

//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;

}

文本变灰

文本textColor变为灰色 rgb的处理有很多这里简单提供一个

    [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];
  }
}

文本变灰色还牵扯到系统颜色的灰色处理，例如[UIcolor whiteColor],系统alertView弹框中的蓝色按钮颜色处理，都需要有专门的处理方法

xib图片变灰

由于xib读取图片不是直接通过[UIimageView imageName:@""] 加载方式 没办法直接通过hook setImage直接设置xib图片变为灰色

方法：重写UIimageView的awakeFromNib，再去执行hook setImage的方法进行加载

webView的变灰

hook webView的初始化方法，注入js灰色

+ (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;
  }

}

attributeText加载htmlString变灰

attribute情况下加载html不是直接通过设置color来改变颜色的，需要通过遍历对应的属性进行重新颜色进行赋值

存在的问题

这样全局修改，可能会把键盘的颜色也改变了需要特殊处理

系统颜色中，alertView中的蓝色，不在定义的系统颜色范围之内需要重新加载

hook系统颜色的处理

完整性

需要完整的私发信息

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