我试图复制苹果公开发布的iOS 7示例屏幕上的模糊背景:
这个问题建议对下面的内容应用CI过滤器，但这是一个完全不同的方法。很明显，iOS 7并没有捕捉到下面视图的内容，原因有很多:
做一些粗略的测试，截取以下视图的截图，并应用CIGaussianBlur过滤器，使用足够大的半径来模拟iOS 7的模糊风格，即使在模拟器上也需要1-2秒。 iOS 7的模糊视图能够模糊动态视图，比如视频或动画，没有明显的延迟。
有没有人可以假设他们可以使用什么框架来创建这种效果，以及是否有可能使用当前的公共api创建类似的效果?
编辑:(来自评论)我们不知道苹果是怎么做的，但我们能做出一些基本的假设吗?我们可以假设他们在使用硬件，对吧?
效果是否在每个视图中都是自包含的，以至于效果实际上不知道它背后是什么?或者，基于模糊的工作原理，模糊背后的内容必须被考虑进去?
如果效果背后的内容是相关的，我们是否可以假设苹果正在接收以下内容的“feed”，并不断地以模糊的方式渲染它们?
当前回答
事实上，我敢打赌这很容易实现。它的运作方式或外观可能不会完全像苹果，但可能非常接近。
首先，你需要确定你要呈现的UIView的CGRect。一旦确定了这一点，就只需要获取UI部分的图像，以便对其进行模糊处理。就像这样……
- (UIImage*)getBlurredImage {
// You will want to calculate this in code based on the view you will be presenting.
CGSize size = CGSizeMake(200,200);
UIGraphicsBeginImageContext(size);
[view drawViewHierarchyInRect:(CGRect){CGPointZero, w, h} afterScreenUpdates:YES]; // view is the view you are grabbing the screen shot of. The view that is to be blurred.
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Gaussian Blur
image = [image applyLightEffect];
// Box Blur
// image = [image boxblurImageWithBlur:0.2f];
return image;
}
高斯模糊-推荐
使用苹果提供的UIImage+ImageEffects Category，你会得到一个高斯模糊，看起来很像iOS 7中的模糊。
盒子模糊
你也可以使用下面的boxBlurImageWithBlur: UIImage类别来使用框模糊。这是基于你可以在这里找到的算法。
@implementation UIImage (Blur)
-(UIImage *)boxblurImageWithBlur:(CGFloat)blur {
if (blur < 0.f || blur > 1.f) {
blur = 0.5f;
}
int boxSize = (int)(blur * 50);
boxSize = boxSize - (boxSize % 2) + 1;
CGImageRef img = self.CGImage;
vImage_Buffer inBuffer, outBuffer;
vImage_Error error;
void *pixelBuffer;
CGDataProviderRef inProvider = CGImageGetDataProvider(img);
CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
inBuffer.width = CGImageGetWidth(img);
inBuffer.height = CGImageGetHeight(img);
inBuffer.rowBytes = CGImageGetBytesPerRow(img);
inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);
pixelBuffer = malloc(CGImageGetBytesPerRow(img) * CGImageGetHeight(img));
if(pixelBuffer == NULL)
NSLog(@"No pixelbuffer");
outBuffer.data = pixelBuffer;
outBuffer.width = CGImageGetWidth(img);
outBuffer.height = CGImageGetHeight(img);
outBuffer.rowBytes = CGImageGetBytesPerRow(img);
error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
if (error) {
NSLog(@"JFDepthView: error from convolution %ld", error);
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(outBuffer.data,
outBuffer.width,
outBuffer.height,
8,
outBuffer.rowBytes,
colorSpace,
kCGImageAlphaNoneSkipLast);
CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
//clean up
CGContextRelease(ctx);
CGColorSpaceRelease(colorSpace);
free(pixelBuffer);
CFRelease(inBitmapData);
CGImageRelease(imageRef);
return returnImage;
}
@end
现在你正在计算要模糊的屏幕区域，将它传递到模糊类别中，并接收一个已经模糊的UIImage，现在剩下的就是将这个模糊的图像设置为你将呈现的视图的背景。就像我说的，这将不是一个完美的匹配苹果正在做的，但它仍然看起来很酷。
希望能有所帮助。
其他回答
您可以尝试使用我的自定义视图，它具有模糊背景的功能。它通过假装拍摄背景快照并模糊它来做到这一点，就像苹果的WWDC代码中那样。使用起来很简单。
我还做了一些改进，在不损失性能的情况下伪造动态模糊。我的视图的背景是一个scrollView，它与视图一起滚动，从而为父视图的其余部分提供了模糊效果。
请参阅我的GitHub上的示例和代码
为什么要麻烦地复制这种效果呢?在你的视图后面画一个UIToolbar。
myView.backgroundColor = [UIColor clearColor];
UIToolbar* bgToolbar = [[UIToolbar alloc] initWithFrame:myView.frame];
bgToolbar.barStyle = UIBarStyleDefault;
[myView.superview insertSubview:bgToolbar belowSubview:myView];
Apple released code at WWDC as a category on UIImage that includes this functionality, if you have a developer account you can grab the UIImage category (and the rest of the sample code) by going to this link: https://developer.apple.com/wwdc/schedule/ and browsing for section 226 and clicking on details. I haven't played around with it yet but I think the effect will be a lot slower on iOS 6, there are some enhancements to iOS 7 that make grabbing the initial screen shot that is used as input to the blur a lot faster.
直接链接:https://developer.apple.com/downloads/download.action?path=wwdc_2013/wwdc_2013_sample_code/ios_uiimageeffects.zip
这是一个解决方案，你可以在WWDC的视频中看到。你必须做高斯模糊，所以你要做的第一件事就是用我在这里写的代码添加一个新的。m和。h文件，然后你要制作和截屏，使用想要的效果并将它添加到你的视图，然后你的UITable UIView或任何必须透明的东西，你可以使用applyBlurWithRadius，来存档想要的效果，这个调用适用于任何UIImage。
最后，模糊的图像将成为背景，上面的其余控件必须是透明的。
为此，你必须添加下面的库:
Acelerate.framework、UIKit.framework CoreGraphics.framework
希望你喜欢。
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;
}
有传言称，苹果工程师声称，为了实现这一性能，他们直接从gpu缓冲区读取，这引发了安全问题，这就是为什么还没有公共API来做这件事。
