Question

如何从WKWebView获取点的RGBA像素颜色？

我有一个UIWebView的工作解决方案，但我想使用WKWebView。当我点击屏幕上的某个点时，我能够从UIWebView中检索RGBA中的颜色值，例如（0,0,0,0），当它是透明的时候（0.76,0.23,0.34,1）它不透明。 WKWebView总是返回（0,0,0,0）。

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我正在开发一个iOS应用程序，其中WebView是最顶级的ui元素。

WebView具有透明的区域，因此您可以看到底层的UIView。

WebView将忽略对透明区域的触摸，而底层的UIView将检索该事件。

因此我确实覆盖了 hitTest 函数：

#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

我的假设是WKWebView有一个不同的CALayer或隐藏的UIView，它绘制实际的网页。

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

此代码修复了我的问题。

iOS WKWebView从点获取RGBA像素颜色

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