如何设置所有的背景透明，使主屏幕可以看到？
我好几天想着这个问题：
如何在应用程序中将所有背景设置为透明，以便可以看到iOS桌面和图标？ 有什么方法可以帮助满足需求吗？ （我仍然没有权力去抽样。）
我已经尝试了一些方法。 我认为整个iOS系统是一个大的应用程序。 当我们在桌面上打开一个应用程序，它将成为一个上层的“视图控制器”，它将覆盖在桌面上。
有了这个想法，我在AppDelegate类中设置了实例variablesAppDelegate ，并且将根视图控制器的背景颜色清除。 但是， 仍然有一个黑色的背景！ 。
任何人都可以帮忙 也许你还没有遇到这个问题，但请思考几秒钟，并提供一些想法。
提前致谢！
不，不可能做到这一点。 如果您尝试为包括UIWindow在内的所有视图组件设置清晰的颜色，则会显示为黑色。
这是您可以在WWDC的video中看到的解决scheme。 你必须做一个高斯模糊，所以你必须做的第一件事是添加一个新的.m和.h文件与我在这里写的代码，然后你必须制作和屏幕拍摄，使用所需的效果和将它添加到你的视图中，然后你的UITable UIView或者任何必须是透明的，你可以使用applyBlurWithRadius来存档所需的效果，这个调用可以与任何UIImage一起使用。
最后，模糊的图像将成为背景，上面的其他控件必须是透明的。
为了这个工作，你必须添加下面的库：
Acelerate.framework，UIKit.framework，CoreGraphics.framework
我希望你喜欢它。
快乐的编码。
//Screen capture. UIGraphicsBeginImageContext(self.view.bounds.size); CGContextRef c = UIGraphicsGetCurrentContext(); CGContextTranslateCTM(c, 0, 0); [self.view.layer renderInContext:c]; UIImage* viewImage = UIGraphicsGetImageFromCurrentImageContext(); viewImage = [viewImage applyLightEffect]; UIGraphicsEndImageContext(); //.h FILE #import <UIKit/UIKit.h> @interface UIImage (ImageEffects) - (UIImage *)applyLightEffect; - (UIImage *)applyExtraLightEffect; - (UIImage *)applyDarkEffect; - (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor; - (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage; @end //.m FILE #import "cGaussianEffect.h" #import <Accelerate/Accelerate.h> #import <float.h> @implementation UIImage (ImageEffects) - (UIImage *)applyLightEffect { UIColor *tintColor = [UIColor colorWithWhite:1.0 alpha:0.3]; return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil]; } - (UIImage *)applyExtraLightEffect { UIColor *tintColor = [UIColor colorWithWhite:0.97 alpha:0.82]; return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil]; } - (UIImage *)applyDarkEffect { UIColor *tintColor = [UIColor colorWithWhite:0.11 alpha:0.73]; return [self applyBlurWithRadius:1 tintColor:tintColor saturationDeltaFactor:1.8 maskImage:nil]; } - (UIImage *)applyTintEffectWithColor:(UIColor *)tintColor { const CGFloat EffectColorAlpha = 0.6; UIColor *effectColor = tintColor; int componentCount = CGColorGetNumberOfComponents(tintColor.CGColor); if (componentCount == 2) { CGFloat b; if ([tintColor getWhite:&b alpha:NULL]) { effectColor = [UIColor colorWithWhite:b alpha:EffectColorAlpha]; } } else { CGFloat r, g, b; if ([tintColor getRed:&r green:&g blue:&b alpha:NULL]) { effectColor = [UIColor colorWithRed:r green:g blue:b alpha:EffectColorAlpha]; } } return [self applyBlurWithRadius:10 tintColor:effectColor saturationDeltaFactor:-1.0 maskImage:nil]; } - (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage { if (self.size.width < 1 || self.size.height < 1) { NSLog (@"*** error: invalid size: (%.2f x %.2f). Both dimensions must be >= 1: %@", self.size.width, self.size.height, self); return nil; } if (!self.CGImage) { NSLog (@"*** error: image must be backed by a CGImage: %@", self); return nil; } if (maskImage && !maskImage.CGImage) { NSLog (@"*** error: maskImage must be backed by a CGImage: %@", maskImage); return nil; } CGRect imageRect = { CGPointZero, self.size }; UIImage *effectImage = self; BOOL hasBlur = blurRadius > __FLT_EPSILON__; BOOL hasSaturationChange = fabs(saturationDeltaFactor - 1.) > __FLT_EPSILON__; if (hasBlur || hasSaturationChange) { UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]); CGContextRef effectInContext = UIGraphicsGetCurrentContext(); CGContextScaleCTM(effectInContext, 1.0, -1.0); CGContextTranslateCTM(effectInContext, 0, -self.size.height); CGContextDrawImage(effectInContext, imageRect, self.CGImage); vImage_Buffer effectInBuffer; effectInBuffer.data = CGBitmapContextGetData(effectInContext); effectInBuffer.width = CGBitmapContextGetWidth(effectInContext); effectInBuffer.height = CGBitmapContextGetHeight(effectInContext); effectInBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectInContext); UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]); CGContextRef effectOutContext = UIGraphicsGetCurrentContext(); vImage_Buffer effectOutBuffer; effectOutBuffer.data = CGBitmapContextGetData(effectOutContext); effectOutBuffer.width = CGBitmapContextGetWidth(effectOutContext); effectOutBuffer.height = CGBitmapContextGetHeight(effectOutContext); effectOutBuffer.rowBytes = CGBitmapContextGetBytesPerRow(effectOutContext); if (hasBlur) { CGFloat inputRadius = blurRadius * [[UIScreen mainScreen] scale]; NSUInteger radius = floor(inputRadius * 3. * sqrt(2 * M_PI) / 4 + 0.5); if (radius % 2 != 1) { radius += 1; } vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend); vImageBoxConvolve_ARGB8888(&effectOutBuffer, &effectInBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend); vImageBoxConvolve_ARGB8888(&effectInBuffer, &effectOutBuffer, NULL, 0, 0, radius, radius, 0, kvImageEdgeExtend); } BOOL effectImageBuffersAreSwapped = NO; if (hasSaturationChange) { CGFloat s = saturationDeltaFactor; CGFloat floatingPointSaturationMatrix[] = { 0.0722 + 0.9278 * s, 0.0722 - 0.0722 * s, 0.0722 - 0.0722 * s, 0, 0.7152 - 0.7152 * s, 0.7152 + 0.2848 * s, 0.7152 - 0.7152 * s, 0, 0.2126 - 0.2126 * s, 0.2126 - 0.2126 * s, 0.2126 + 0.7873 * s, 0, 0, 0, 0, 1, }; const int32_t divisor = 256; NSUInteger matrixSize = sizeof(floatingPointSaturationMatrix)/sizeof(floatingPointSaturationMatrix[0]); int16_t saturationMatrix[matrixSize]; for (NSUInteger i = 0; i < matrixSize; ++i) { saturationMatrix[i] = (int16_t)roundf(floatingPointSaturationMatrix[i] * divisor); } if (hasBlur) { vImageMatrixMultiply_ARGB8888(&effectOutBuffer, &effectInBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags); effectImageBuffersAreSwapped = YES; } else { vImageMatrixMultiply_ARGB8888(&effectInBuffer, &effectOutBuffer, saturationMatrix, divisor, NULL, NULL, kvImageNoFlags); } } if (!effectImageBuffersAreSwapped) effectImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); if (effectImageBuffersAreSwapped) effectImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); } UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]); CGContextRef outputContext = UIGraphicsGetCurrentContext(); CGContextScaleCTM(outputContext, 1.0, -1.0); CGContextTranslateCTM(outputContext, 0, -self.size.height); CGContextDrawImage(outputContext, imageRect, self.CGImage); if (hasBlur) { CGContextSaveGState(outputContext); if (maskImage) { CGContextClipToMask(outputContext, imageRect, maskImage.CGImage); } CGContextDrawImage(outputContext, imageRect, effectImage.CGImage); CGContextRestoreGState(outputContext); } if (tintColor) { CGContextSaveGState(outputContext); CGContextSetFillColorWithColor(outputContext, tintColor.CGColor); CGContextFillRect(outputContext, imageRect); CGContextRestoreGState(outputContext); } UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return outputImage; }