iOS 毛玻璃效果
2013-11-22 16:13
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- (UIImage *)applyBlurWithRadius:(CGFloat)blurRadius tintColor:(UIColor *)tintColor saturationDeltaFactor:(CGFloat)saturationDeltaFactor maskImage:(UIImage *)maskImage { if (CHECK_IOS() >= 50) { // Check pre-conditions. 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) { // A description of how to compute the box kernel width from the Gaussian // radius (aka standard deviation) appears in the SVG spec: // http://www.w3.org/TR/SVG/filters.html#feGaussianBlurElement // // For larger values of 's' (s >= 2.0), an approximation can be used: Three // successive box-blurs build a piece-wise quadratic convolution kernel, which // approximates the Gaussian kernel to within roughly 3%. // // let d = floor(s * 3*sqrt(2*pi)/4 + 0.5) // // ... if d is odd, use three box-blurs of size 'd', centered on the output pixel. // CGFloat inputRadius = blurRadius * [[UIScreen mainScreen] scale]; NSUInteger radius = floor(inputRadius * 3. * sqrt(2 * M_PI) / 4 + 0.5); if (radius % 2 != 1) { radius += 1; // force radius to be odd so that the three box-blur methodology works. } 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(); } // Set up output context. UIGraphicsBeginImageContextWithOptions(self.size, NO, [[UIScreen mainScreen] scale]); CGContextRef outputContext = UIGraphicsGetCurrentContext(); CGContextScaleCTM(outputContext, 1.0, -1.0); CGContextTranslateCTM(outputContext, 0, -self.size.height); // Draw base image. CGContextDrawImage(outputContext, imageRect, self.CGImage); // Draw effect image. if (hasBlur) { CGContextSaveGState(outputContext); if (maskImage) { CGContextClipToMask(outputContext, imageRect, maskImage.CGImage); } CGContextDrawImage(outputContext, imageRect, effectImage.CGImage); CGContextRestoreGState(outputContext); } // Add in color tint. if (tintColor) { CGContextSaveGState(outputContext); CGContextSetFillColorWithColor(outputContext, tintColor.CGColor); CGContextFillRect(outputContext, imageRect); CGContextRestoreGState(outputContext); } // Output image is ready. UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return outputImage; } return self; }
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