Ios 缩放图像:加速如何成为最慢的方法?
我正在测试几种方法来重新缩放UIImage 我已经测试了所有这些方法,并测量了它们调整图像大小所需的时间 1)UIGraphicsBeginImageContextWithOptions&UIImage-drawInRect:Ios 缩放图像:加速如何成为最慢的方法?,ios,uiimage,core-graphics,core-image,ciimage,Ios,Uiimage,Core Graphics,Core Image,Ciimage,我正在测试几种方法来重新缩放UIImage 我已经测试了所有这些方法,并测量了它们调整图像大小所需的时间 1)UIGraphicsBeginImageContextWithOptions&UIImage-drawInRect: let image = UIImage(contentsOfFile: self.URL.path!) let size = CGSizeApplyAffineTransform(image.size, CGAffineTransformMakeScale(0.5, 0
let image = UIImage(contentsOfFile: self.URL.path!)
let size = CGSizeApplyAffineTransform(image.size, CGAffineTransformMakeScale(0.5, 0.5))
let hasAlpha = false
let scale: CGFloat = 0.0 // Automatically use scale factor of main screen
UIGraphicsBeginImageContextWithOptions(size, !hasAlpha, scale)
image.drawInRect(CGRect(origin: CGPointZero, size: size))
let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
2)CGBitmapContextCreate和CGContextDrawImage
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
let width = CGImageGetWidth(cgImage) / 2
let height = CGImageGetHeight(cgImage) / 2
let bitsPerComponent = CGImageGetBitsPerComponent(cgImage)
let bytesPerRow = CGImageGetBytesPerRow(cgImage)
let colorSpace = CGImageGetColorSpace(cgImage)
let bitmapInfo = CGImageGetBitmapInfo(cgImage)
let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo.rawValue)
CGContextSetInterpolationQuality(context, kCGInterpolationHigh)
CGContextDrawImage(context, CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(width), height: CGFloat(height))), cgImage)
let scaledImage = CGBitmapContextCreateImage(context).flatMap { UIImage(CGImage: $0) }
let image = CIImage(contentsOfURL: self.URL)
let filter = CIFilter(name: "CILanczosScaleTransform")!
filter.setValue(image, forKey: "inputImage")
filter.setValue(0.5, forKey: "inputScale")
filter.setValue(1.0, forKey: "inputAspectRatio")
let outputImage = filter.valueForKey("outputImage") as! CIImage
let context = CIContext(options: [kCIContextUseSoftwareRenderer: false])
let scaledImage = UIImage(CGImage: self.context.createCGImage(outputImage, fromRect: outputImage.extent()))
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
// create a source buffer
var format = vImage_CGImageFormat(bitsPerComponent: 8, bitsPerPixel: 32, colorSpace: nil,
bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.First.rawValue),
version: 0, decode: nil, renderingIntent: CGColorRenderingIntent.RenderingIntentDefault)
var sourceBuffer = vImage_Buffer()
defer {
sourceBuffer.data.dealloc(Int(sourceBuffer.height) * Int(sourceBuffer.height) * 4)
}
var error = vImageBuffer_InitWithCGImage(&sourceBuffer, &format, nil, cgImage, numericCast(kvImageNoFlags))
guard error == kvImageNoError else { return nil }
// create a destination buffer
let scale = UIScreen.mainScreen().scale
let destWidth = Int(image.size.width * 0.5 * scale)
let destHeight = Int(image.size.height * 0.5 * scale)
let bytesPerPixel = CGImageGetBitsPerPixel(image.CGImage) / 8
let destBytesPerRow = destWidth * bytesPerPixel
let destData = UnsafeMutablePointer<UInt8>.alloc(destHeight * destBytesPerRow)
defer {
destData.dealloc(destHeight * destBytesPerRow)
}
var destBuffer = vImage_Buffer(data: destData, height: vImagePixelCount(destHeight), width: vImagePixelCount(destWidth), rowBytes: destBytesPerRow)
// scale the image
error = vImageScale_ARGB8888(&sourceBuffer, &destBuffer, nil, numericCast(kvImageHighQualityResampling))
guard error == kvImageNoError else { return nil }
// create a CGImage from vImage_Buffer
let destCGImage = vImageCreateCGImageFromBuffer(&destBuffer, &format, nil, nil, numericCast(kvImageNoFlags), &error)?.takeRetainedValue()
guard error == kvImageNoError else { return nil }
// create a UIImage
let scaledImage = destCGImage.flatMap { UIImage(CGImage: $0, scale: 0.0, orientation: image.imageOrientation) }
3)CGImageSourceCreateTumbnailAtIndex
import ImageIO
if let imageSource = CGImageSourceCreateWithURL(self.URL, nil) {
let options: [NSString: NSObject] = [
kCGImageSourceThumbnailMaxPixelSize: max(size.width, size.height) / 2.0,
kCGImageSourceCreateThumbnailFromImageAlways: true
]
let scaledImage = CGImageSourceCreateThumbnailAtIndex(imageSource, 0, options).flatMap { UIImage(CGImage: $0) }
}
4)Lanczos使用核心图像重新采样
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
let width = CGImageGetWidth(cgImage) / 2
let height = CGImageGetHeight(cgImage) / 2
let bitsPerComponent = CGImageGetBitsPerComponent(cgImage)
let bytesPerRow = CGImageGetBytesPerRow(cgImage)
let colorSpace = CGImageGetColorSpace(cgImage)
let bitmapInfo = CGImageGetBitmapInfo(cgImage)
let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo.rawValue)
CGContextSetInterpolationQuality(context, kCGInterpolationHigh)
CGContextDrawImage(context, CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(width), height: CGFloat(height))), cgImage)
let scaledImage = CGBitmapContextCreateImage(context).flatMap { UIImage(CGImage: $0) }
let image = CIImage(contentsOfURL: self.URL)
let filter = CIFilter(name: "CILanczosScaleTransform")!
filter.setValue(image, forKey: "inputImage")
filter.setValue(0.5, forKey: "inputScale")
filter.setValue(1.0, forKey: "inputAspectRatio")
let outputImage = filter.valueForKey("outputImage") as! CIImage
let context = CIContext(options: [kCIContextUseSoftwareRenderer: false])
let scaledImage = UIImage(CGImage: self.context.createCGImage(outputImage, fromRect: outputImage.extent()))
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
// create a source buffer
var format = vImage_CGImageFormat(bitsPerComponent: 8, bitsPerPixel: 32, colorSpace: nil,
bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.First.rawValue),
version: 0, decode: nil, renderingIntent: CGColorRenderingIntent.RenderingIntentDefault)
var sourceBuffer = vImage_Buffer()
defer {
sourceBuffer.data.dealloc(Int(sourceBuffer.height) * Int(sourceBuffer.height) * 4)
}
var error = vImageBuffer_InitWithCGImage(&sourceBuffer, &format, nil, cgImage, numericCast(kvImageNoFlags))
guard error == kvImageNoError else { return nil }
// create a destination buffer
let scale = UIScreen.mainScreen().scale
let destWidth = Int(image.size.width * 0.5 * scale)
let destHeight = Int(image.size.height * 0.5 * scale)
let bytesPerPixel = CGImageGetBitsPerPixel(image.CGImage) / 8
let destBytesPerRow = destWidth * bytesPerPixel
let destData = UnsafeMutablePointer<UInt8>.alloc(destHeight * destBytesPerRow)
defer {
destData.dealloc(destHeight * destBytesPerRow)
}
var destBuffer = vImage_Buffer(data: destData, height: vImagePixelCount(destHeight), width: vImagePixelCount(destWidth), rowBytes: destBytesPerRow)
// scale the image
error = vImageScale_ARGB8888(&sourceBuffer, &destBuffer, nil, numericCast(kvImageHighQualityResampling))
guard error == kvImageNoError else { return nil }
// create a CGImage from vImage_Buffer
let destCGImage = vImageCreateCGImageFromBuffer(&destBuffer, &format, nil, nil, numericCast(kvImageNoFlags), &error)?.takeRetainedValue()
guard error == kvImageNoError else { return nil }
// create a UIImage
let scaledImage = destCGImage.flatMap { UIImage(CGImage: $0, scale: 0.0, orientation: image.imageOrientation) }
5)加速过程中的振动
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
let width = CGImageGetWidth(cgImage) / 2
let height = CGImageGetHeight(cgImage) / 2
let bitsPerComponent = CGImageGetBitsPerComponent(cgImage)
let bytesPerRow = CGImageGetBytesPerRow(cgImage)
let colorSpace = CGImageGetColorSpace(cgImage)
let bitmapInfo = CGImageGetBitmapInfo(cgImage)
let context = CGBitmapContextCreate(nil, width, height, bitsPerComponent, bytesPerRow, colorSpace, bitmapInfo.rawValue)
CGContextSetInterpolationQuality(context, kCGInterpolationHigh)
CGContextDrawImage(context, CGRect(origin: CGPointZero, size: CGSize(width: CGFloat(width), height: CGFloat(height))), cgImage)
let scaledImage = CGBitmapContextCreateImage(context).flatMap { UIImage(CGImage: $0) }
let image = CIImage(contentsOfURL: self.URL)
let filter = CIFilter(name: "CILanczosScaleTransform")!
filter.setValue(image, forKey: "inputImage")
filter.setValue(0.5, forKey: "inputScale")
filter.setValue(1.0, forKey: "inputAspectRatio")
let outputImage = filter.valueForKey("outputImage") as! CIImage
let context = CIContext(options: [kCIContextUseSoftwareRenderer: false])
let scaledImage = UIImage(CGImage: self.context.createCGImage(outputImage, fromRect: outputImage.extent()))
let cgImage = UIImage(contentsOfFile: self.URL.path!).CGImage
// create a source buffer
var format = vImage_CGImageFormat(bitsPerComponent: 8, bitsPerPixel: 32, colorSpace: nil,
bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.First.rawValue),
version: 0, decode: nil, renderingIntent: CGColorRenderingIntent.RenderingIntentDefault)
var sourceBuffer = vImage_Buffer()
defer {
sourceBuffer.data.dealloc(Int(sourceBuffer.height) * Int(sourceBuffer.height) * 4)
}
var error = vImageBuffer_InitWithCGImage(&sourceBuffer, &format, nil, cgImage, numericCast(kvImageNoFlags))
guard error == kvImageNoError else { return nil }
// create a destination buffer
let scale = UIScreen.mainScreen().scale
let destWidth = Int(image.size.width * 0.5 * scale)
let destHeight = Int(image.size.height * 0.5 * scale)
let bytesPerPixel = CGImageGetBitsPerPixel(image.CGImage) / 8
let destBytesPerRow = destWidth * bytesPerPixel
let destData = UnsafeMutablePointer<UInt8>.alloc(destHeight * destBytesPerRow)
defer {
destData.dealloc(destHeight * destBytesPerRow)
}
var destBuffer = vImage_Buffer(data: destData, height: vImagePixelCount(destHeight), width: vImagePixelCount(destWidth), rowBytes: destBytesPerRow)
// scale the image
error = vImageScale_ARGB8888(&sourceBuffer, &destBuffer, nil, numericCast(kvImageHighQualityResampling))
guard error == kvImageNoError else { return nil }
// create a CGImage from vImage_Buffer
let destCGImage = vImageCreateCGImageFromBuffer(&destBuffer, &format, nil, nil, numericCast(kvImageNoFlags), &error)?.takeRetainedValue()
guard error == kvImageNoError else { return nil }
// create a UIImage
let scaledImage = destCGImage.flatMap { UIImage(CGImage: $0, scale: 0.0, orientation: image.imageOrientation) }
让cgImage=UIImage(contentsOfFile:self.URL.path!).cgImage
//创建源缓冲区
var format=vImage_CGImageFormat(比特分量:8,比特像素:32,颜色空间:nil,
bitmapInfo:CGBitmapInfo(rawValue:CGImageAlphaInfo.First.rawValue),
版本:0,解码:nil,renderingIntent:CGColorRenderingIntent.RenderingIntentDefault)
var sourceBuffer=vImage_Buffer()
推迟{
sourceBuffer.data.dealoc(Int(sourceBuffer.height)*Int(sourceBuffer.height)*4)
}
var error=vImageBuffer_InitWithCGImage(&sourceBuffer,&format,nil,cgImage,numericCast(kvImageNoFlags))
保护错误==kvImageNoError else{return nil}
//创建目标缓冲区
让scale=UIScreen.mainScreen().scale
设destWidth=Int(image.size.width*0.5*比例)
设destHeight=Int(image.size.height*0.5*比例)
让bytesPerPixel=cgmagegetbitsperpixel(image.CGImage)/8
设destBytesPerRow=destWidth*bytesPerPixel
设destData=UnsafeMutablePointer.alloc(destwheight*destBytesPerRow)
推迟{
destData.dealloc(destHeight*destBytesPerRow)
}
var destBuffer=vImage_Buffer(数据:destData,高度:vImagePixelCount(destHeight),宽度:vImagePixelCount(destWidth),行字节:destBytesPerRow)
//缩放图像
错误=vImageScale_argb888(&sourceBuffer,&destBuffer,nil,数值广播(kvImageHighQualityResampling))
保护错误==kvImageNoError else{return nil}
//从vImage_缓冲区创建CGImage
设destCGImage=VimageCreateCImageFromBuffer(&destBuffer,&format,nil,nil,numericCast(kImageNoFlags),&error)?。takeRetainedValue()
保护错误==kvImageNoError else{return nil}
//创建一个UIImage
设scaleImage=destCGImage.flatMap{UIImage(CGImage:$0,比例:0.0,方向:image.imageOrientation)}
经过数小时的测试,并测量每种方法将图像重新缩放到100x100所需的时间,我的结论与NSHipster完全不同。首先,accelerate中的vImage比第一种方法慢200倍,在我看来,它是其他方法的可怜表亲。核心图像方法也很慢。但我很好奇方法1是如何粉碎方法3、4和5的,其中一些理论上是在GPU上处理东西的
例如,方法#3花了2秒钟将1024x1024图像的大小调整为100x100。另一方面#1花了0.01秒
我错过什么了吗
一定是出了什么问题,否则苹果不会花时间写加速和CIImage之类的东西
注意:我正在测量从图像已加载到变量到缩放版本保存到另一个变量的时间。我不考虑从文件中读取所需的时间。由于各种原因,加速可能是最慢的方法:
如果你真的认为加速在这里太离谱了,那就提交一个bug。不过,在这样做之前,我肯定会检查Instruments Time Profile,您在基准测试循环中花费了大部分时间在vImageScale上。我很惊讶其中一些方法居然奏效:
UIImage(contentsOfFile:self.URL.absoluteString!)
不正确。它应该是UIImage(contentsOfFile:self.URL.path!)
或UIImage(contentsOfURL:self.URL)
。您比较过所有这些方法的输出吗?结果输出是否相同?所有情况下尺寸相同?结果相同。代码可能包含一些输入错误。我已经解决了这个问题。也可以在MetalPerformanceShader中尝试MPSImageScale。我有一个类似的结果,vImage缩放非常慢。您没有按照vImage编程指南中的建议重新使用自己的临时缓冲区进行重采样操作,即:vImageScale_argb888(&sourceBuffer,&destBuffer,nil,numericCast(kvImageHighQualityResampling))中的nil参数然而,在我的案例中,我确实使用了这项技术,但在性能上只获得了非常温和且微不足道的改进。