如何在Go中快速缩放和锐化图像？

huangapple
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英文:

How can I quickly scale and sharpen an image in Go?

问题

我目前正在将一个相当基本的相册应用程序从PHP移植到Go。该应用程序具有自动生成每个图像的缩略图和中等大小版本的功能。

在PHP中，我使用了GD库，因为它内置并且工作得很好（代码在问题的末尾）。我以为我可以在Go中复制这个功能，并在https://github.com/bolknote/go-gd中找到了go-gd（同样的代码在末尾）。它可以工作，但速度大约慢了10倍（使用time wget $URL进行测量）。PHP实现从10 MP图像生成一个1024x768版本大约需要1秒钟，而Go代码则需要近10秒钟。

有没有办法加快速度，或者有没有其他在Go中实现缩放和卷积的图像处理库，同时速度还相对较快？

PHP代码

  1. public function saveThumb($outName, $options) {
  2.     $this->img = imagecreatefromjpeg($filename);
  3.     if (!is_dir(dirname($outName))) {
  4.         mkdir(dirname($outName), 0777, true);
  5.     }
  6.     
  7.     $width = imagesx($this->img);
  8.     $height = imagesy($this->img);
  9.     
  10.     if ($options["keep_aspect"]) {
  11.         $factor = min($options["size_x"]/$width, $options["size_y"]/$height);
  12.         $new_width = round($factor*$width);
  13.         $new_height = round($factor*$height);
  14.     } else {
  15.         $new_width  = $options["size_x"];
  16.         $new_height = $options["size_y"];
  17.     }
  18.     
  19.     // create a new temporary image
  20.     $tmp_img = imagecreatetruecolor($new_width, $new_height);
  22.     // copy and resize old image into new image
  23.     imagecopyresampled($tmp_img, $this->img, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
  24.     
  25.     if ($options["sharpen"]) {
  26.         // define the sharpen matrix
  27.         $sharpen = array(
  28.             array(-1, -1.7, -1),
  29.             array(-1.7, 20, -1.7),
  30.             array(-1, -1.7, -1) 
  31.         );
  33.         // calculate the sharpen divisor
  34.         $divisor = array_sum(array_map('array_sum', $sharpen));
  36.         // apply the matrix
  37.         imageconvolution($tmp_img, $sharpen, $divisor, 0);
  38.     }
  40.     // save thumbnail into a file
  41.     imagejpeg($tmp_img, $outName);     
  42. }

Go代码

  1. func (entry *entry) GenerateThumb(options ImageType, overwrite bool) os.Error {
  2.     targetFilename := entry.Filename(imageType)
  3.     sourceFilename := entry.Filename(IMAGE_TYPE_FULL)
  4.     targetDirname, _ := filepath.Split(targetFilename)
  5.     os.MkdirAll(targetDirname, 0777)
  7.     targetFi, errT := os.Stat(targetFilename)
  8.     sourceFi, errS := os.Stat(sourceFilename)
  10.     image := gd.CreateFromJpeg(sourceFilename)
  11.     if image == nil {
  12.         return os.NewError("Image could not be loaded")
  13.     }
  15.     var targetX, targetY int = 0, 0
  17.     if options.KeepAspect {
  18.         factor := math.Fmin(float64(options.SizeX)/float64(image.Sx()), float64(options.SizeY)/float64(image.Sy()))
  19.         targetX = int(factor*float64(image.Sx()))
  20.         targetY = int(factor*float64(image.Sy()))
  21.     } else {
  22.         targetX = options.SizeX
  23.         targetY = options.SizeY
  24.     }
  25.     tmpImage := gd.CreateTrueColor(targetX, targetY)
  26.     image.CopyResampled(tmpImage, 0, 0, 0, 0, tmpImage.Sx(), tmpImage.Sy(), image.Sx(), image.Sy())
  28.     if options.Sharpen {
  29.         sharpenMatrix := [3][3]float32{
  30.     	{-1, -1.7, -1},
  31.     	{-1.7, 20, -1.7},
  32.     	{-1, -1.7, -1} }
  33.         tmpImage.Convolution(sharpenMatrix, 9.2, 0)
  34.     }
  35.     tmpImage.Jpeg(targetFilename, 90)
  37.     return nil
  38. }

编辑：使用resize.go的Go代码（参见答案）

  1. func (entry *entry) GenerateThumb(options ImageType, overwrite bool) os.Error {
  2.     targetFilename := entry.Filename(imageType)
  3.     sourceFilename := entry.Filename(IMAGE_TYPE_FULL)
  4.     targetDirname, _ := filepath.Split(targetFilename)
  5.     os.MkdirAll(targetDirname, 0777)
  6.     
  7.     targetFi, errT := os.Stat(targetFilename)
  8.     sourceFi, errS := os.Stat(sourceFilename)
  9.     
  10.     if errT == nil && errS == nil {
  11. 	    if targetFi.Mtime_ns > sourceFi.Mtime_ns && !overwrite {
  12. 		    // already up-to-date, nothing to do
  13. 		    return nil
  14. 	    }
  15.     }
  16.     
  17.     log.Printf("Generate(\"%v\", %v)\n", imageType, overwrite)
  19.     inFile, fErr := os.Open(sourceFilename)
  20.     if fErr != nil {
  21. 	    log.Fatal(fErr)
  22.     }
  23.     defer inFile.Close()
  25.     img, _, err := image.Decode(inFile)
  26.     if err != nil {
  27. 	    log.Fatal(err)
  28.     }
  29.     
  30.     var targetX, targetY int
  31.     if options.KeepAspect {
  32. 	    factor := math.Fmin(float64(options.SizeX)/float64(img.Bounds().Max.X), float64(options.SizeY)/float64(img.Bounds().Max.Y))
  33. 	    targetX = int(factor*float64(img.Bounds().Max.X))
  34. 	    targetY = int(factor*float64(img.Bounds().Max.Y))
  35.     } else {
  36. 	    targetX = curType.SizeX
  37. 	    targetY = curType.SizeY
  38.     }
  39.     newImg := resize.Resample(img, image.Rect(0, 0, img.Bounds().Max.X, img.Bounds().Max.Y), targetX, targetY)
  41.     var outFile *os.File
  42.     outFile, fErr = os.Create(targetFilename)
  43.     if fErr != nil {
  44. 	    log.Fatal(fErr)
  45.     }
  46.     defer outFile.Close()
  48.     err = jpeg.Encode(outFile, newImg, &jpeg.Options{90})
  49.     if err != nil {
  50. 	    log.Fatal(err)
  51.     }
  52.     return nil
  53. }
英文:

I'm currently porting a pretty basic gallery application from PHP to Go. This application features automatic generation of thumbnails and middle-sized version of every image.

In PHP I used GD, because it ships with it and worked pretty well. (Code is at the end of the question). I thought I could just replicate that in Go and found go-gd from https://github.com/bolknote/go-gd (again, code is at the end). It works, but it is roughly 10 times slower (measured using time wget $URL). The PHP implementation takes about 1 second for generating a 1024x768 version from a 10 MP-image, while the Go-Code takes almost 10 seconds.

Is there any way to speed this up or any other image-processing libary for Go, which implements scaling and convolution while being reasonably fast?

PHP-Code

  1. public function saveThumb($outName, $options) {
  2.     $this->img = imagecreatefromjpeg($filename);
  3.     if (!is_dir(dirname($outName))) {
  4.         mkdir(dirname($outName), 0777, true);
  5.     }
  6.     
  7.     $width = imagesx($this->img);
  8.     $height = imagesy($this->img);
  9.     
  10.     if ($options["keep_aspect"]) {
  11.         $factor = min($options["size_x"]/$width, $options["size_y"]/$height);
  12.         $new_width = round($factor*$width);
  13.         $new_height = round($factor*$height);
  14.     } else {
  15.         $new_width  = $options["size_x"];
  16.         $new_height = $options["size_y"];
  17.     }
  18.     
  19.     // create a new temporary image
  20.     $tmp_img = imagecreatetruecolor($new_width, $new_height);
  22.     // copy and resize old image into new image
  23.     imagecopyresampled($tmp_img, $this->img, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
  24.     
  25.     if ($options["sharpen"]) {
  26.         // define the sharpen matrix
  27.         $sharpen = array(
  28.             array(-1, -1.7, -1),
  29.             array(-1.7, 20, -1.7),
  30.             array(-1, -1.7, -1) 
  31.         );
  33.         // calculate the sharpen divisor
  34.         $divisor = array_sum(array_map('array_sum', $sharpen));
  36.         // apply the matrix
  37.         imageconvolution($tmp_img, $sharpen, $divisor, 0);
  38.     }
  40.     // save thumbnail into a file
  41.     imagejpeg($tmp_img, $outName);     
  42. }

Go-Code

  1. func (entry *entry) GenerateThumb(options ImageType, overwrite bool) os.Error {
  2.     targetFilename := entry.Filename(imageType)
  3.     sourceFilename := entry.Filename(IMAGE_TYPE_FULL)
  4.     targetDirname, _ := filepath.Split(targetFilename)
  5.     os.MkdirAll(targetDirname, 0777)
  7.     targetFi, errT := os.Stat(targetFilename)
  8.     sourceFi, errS := os.Stat(sourceFilename)
  10.     image := gd.CreateFromJpeg(sourceFilename)
  11.     if image == nil {
  12.         return os.NewError("Image could not be loaded")
  13.     }
  15.     var targetX, targetY int = 0, 0
  17.     if options.KeepAspect {
  18.         factor := math.Fmin(float64(options.SizeX)/float64(image.Sx()), float64(options.SizeY)/float64(image.Sy()))
  19.         targetX = int(factor*float64(image.Sx()))
  20.         targetY = int(factor*float64(image.Sy()))
  21.     } else {
  22.         targetX = options.SizeX
  23.         targetY = options.SizeY
  24.     }
  25.     tmpImage := gd.CreateTrueColor(targetX, targetY)
  26.     image.CopyResampled(tmpImage, 0, 0, 0, 0, tmpImage.Sx(), tmpImage.Sy(), image.Sx(), image.Sy())
  28.     if options.Sharpen {
  29.         sharpenMatrix := [3][3]float32{
  30.     	{-1, -1.7, -1},
  31.     	{-1.7, 20, -1.7},
  32.     	{-1, -1.7, -1} }
  33.         tmpImage.Convolution(sharpenMatrix, 9.2, 0)
  34.     }
  35.     tmpImage.Jpeg(targetFilename, 90)
  37.     return nil
  38. }

EDIT: Go-Code using resize.go (see answer)

  1. func (entry *entry) GenerateThumb(options ImageType, overwrite bool) os.Error {
  2.     targetFilename := entry.Filename(imageType)
  3.     sourceFilename := entry.Filename(IMAGE_TYPE_FULL)
  4.     targetDirname, _ := filepath.Split(targetFilename)
  5.     os.MkdirAll(targetDirname, 0777)
  6.     
  7.     targetFi, errT := os.Stat(targetFilename)
  8.     sourceFi, errS := os.Stat(sourceFilename)
  9.     
  10.     if errT == nil && errS == nil {
  11. 	    if targetFi.Mtime_ns > sourceFi.Mtime_ns && !overwrite {
  12. 		    // already up-to-date, nothing to do
  13. 		    return nil
  14. 	    }
  15.     }
  16.     
  17.     log.Printf("Generate(\"%v\", %v)\n", imageType, overwrite)
  19.     inFile, fErr := os.Open(sourceFilename)
  20.     if fErr != nil {
  21. 	    log.Fatal(fErr)
  22.     }
  23.     defer inFile.Close()
  25.     img, _, err := image.Decode(inFile)
  26.     if err != nil {
  27. 	    log.Fatal(err)
  28.     }
  29.     
  30.     var targetX, targetY int
  31.     if options.KeepAspect {
  32. 	    factor := math.Fmin(float64(options.SizeX)/float64(img.Bounds().Max.X), float64(options.SizeY)/float64(img.Bounds().Max.Y))
  33. 	    targetX = int(factor*float64(img.Bounds().Max.X))
  34. 	    targetY = int(factor*float64(img.Bounds().Max.Y))
  35.     } else {
  36. 	    targetX = curType.SizeX
  37. 	    targetY = curType.SizeY
  38.     }
  39.     newImg := resize.Resample(img, image.Rect(0, 0, img.Bounds().Max.X, img.Bounds().Max.Y), targetX, targetY)
  41.     var outFile *os.File
  42.     outFile, fErr = os.Create(targetFilename)
  43.     if fErr != nil {
  44. 	    log.Fatal(fErr)
  45.     }
  46.     defer outFile.Close()
  48.     err = jpeg.Encode(outFile, newImg, &jpeg.Options{90})
  49.     if err != nil {
  50. 	    log.Fatal(err)
  51.     }
  52.     return nil
  53. }

答案1

得分: 6

你应该查看这个调整大小的库：github.com/nfnt/resize。它有6个好的插值函数可供选择。

英文:

You should check out this resize library: github.com/nfnt/resize. It has 6 good interpolation functions to choose from.

答案2

得分: 3

The Moustachio example application for GAE by Andrew Gerrand contains a resize.go file with a native Go implementation. There was also a similar question on the go-nuts mailing list some days ago and Nigel has posted an updated version of this file there. You might want to try it 如何在Go中快速缩放和锐化图像？

英文:

The Moustachio example application for GAE by Andrew Gerrand contains a resize.go file with a native Go implementation. There was also a similar question on the go-nuts mailing list some days ago and Nigel has posted an updated version of this file there. You might want to try it 如何在Go中快速缩放和锐化图像？

答案3

得分: 0

最简单的解决方案似乎是将图像保存到磁盘，并使用Image Magic的convert命令进行转换。如果您想要额外的性能，可以使用内存磁盘。

英文:

The easiest solution seems to save the image to disk, and execute convert from Image Magic to transform it. You can use a ram disk if you want extra performance.

huangapple
  • 本文由 发表于 2011年9月5日 22:19:36
  • 转载请务必保留本文链接：https://go.coder-hub.com/7309355.html
  • go
  • image-processing
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