iOS WKWebView從點得到RGBA像素顏色

Question

如何從WKWebView獲取點的RGBA像素顏色？

我有一個UIWebView的工作解決方案，但我想使用WKWebView代替。當我點擊屏幕上的一個點時，我可以從UIWebView中檢索RGBA中的顏色值，例如（0,0,0,0），當它透明或類似的時候（0.76,0.23,0.34,1）它不透明。 WKWebView總是返回（0,0,0,0）。

更多細節

我工作的iOS應用程序具有的WebView作爲最頂級的UI元素。

WebView具有透明的區域，以便您可以看到底層的UIView。

WebView應忽略透明區域上的觸摸，而底層UIView應該檢索事件。

爲此我做了覆蓋則hitTest功能：

#import "OverlayView.h" 
#import <QuartzCore/QuartzCore.h> 

@implementation OverlayView 

-(UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event { 

    UIView* subview = [super hitTest:point withEvent:event]; // this will always be a webview 

    if ([self isTransparent:point fromView:subview.layer]) // if point is transparent then let superview deal with it 
    { 
     return [self superview]; 
    } 

    return subview; // return webview 
} 

- (BOOL) isTransparent:(CGPoint)point fromView:(CALayer*)layer 
{ 
    unsigned char pixel[4] = {0}; 

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    CGContextRef context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, colorSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast); 

    CGContextTranslateCTM(context, -point.x, -point.y); 

    [layer renderInContext:context]; 

    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace); 

    return (pixel[0]/255.0 == 0) &&(pixel[1]/255.0 == 0) &&(pixel[2]/255.0 == 0) &&(pixel[3]/255.0 == 0) ; 
} 

@end 

我的假設是，WKWebView有不同的CALayer或隱藏的UIView它繪製實際的網頁來。

Answer 1

#import "OverlayView.h" 
#import <QuartzCore/QuartzCore.h> 

@implementation OverlayView 

-(UIView*)hitTest:(CGPoint)point withEvent:(UIEvent*)event { 

    UIView* subview = [super hitTest:point withEvent:event]; // this should always be a webview 

    if ([self isTransparent:[self convertPoint:point toView:subview] fromView:subview.layer]) // if point is transparent then let superview deal with it 
    { 
     return [self superview]; 
    } 

    return subview; // return webview 
} 

- (BOOL) isTransparent:(CGPoint)point fromView:(CALayer*)layer 
{ 
    unsigned char pixel[4] = {0}; 

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    CGContextRef context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, colorSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast); 

    CGContextTranslateCTM(context, -point.x, -point.y); 

    UIGraphicsPushContext(context); 
    [self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES]; 
    UIGraphicsPopContext(); 

    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace); 

    return (pixel[0]/255.0 == 0) &&(pixel[1]/255.0 == 0) &&(pixel[2]/255.0 == 0) &&(pixel[3]/255.0 == 0) ; 
} 

@end 

此代碼解決了我的問題。