如何使用jpegoptim来拥有只有20 in大小的文件？

Question

我试过使用jpegoptim，甚至尝试过这个命令，但都很困惑。这里有一个文件我想减少到50k，甚至可以降低数据的质量-

Image:
  Filename: shirish.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Mime type: image/jpeg
  Class: DirectClass
  Geometry: 4624x3468+0+0
  Resolution: 72x72
  Print size: 64.2222x48.1667
  Units: PixelsPerInch
  Colorspace: sRGB
  Type: TrueColor
  Base type: Undefined
  Endianness: Undefined
  Depth: 8-bit
  Channel depth:
    red: 8-bit
    green: 8-bit
    blue: 8-bit
  Channel statistics:
    Pixels: 16036032
    Red:
      min: 0  (0)
      max: 255 (1)
      mean: 119.779 (0.46972)
      standard deviation: 60.359 (0.236702)
      kurtosis: -1.33094
      skewness: -0.2895
      entropy: 0.920909
    Green:
      min: 0  (0)
      max: 255 (1)
      mean: 115.071 (0.45126)
      standard deviation: 63.5402 (0.249177)
      kurtosis: -1.51367
      skewness: -0.162973
      entropy: 0.912909
    Blue:
      min: 0  (0)
      max: 255 (1)
      mean: 114.566 (0.449277)
      standard deviation: 61.8685 (0.242621)
      kurtosis: -1.51015
      skewness: -0.101152
      entropy: 0.912805
  Image statistics:
    Overall:
      min: 0  (0)
      max: 255 (1)
      mean: 116.472 (0.456752)
      standard deviation: 61.9226 (0.242834)
      kurtosis: -1.46062
      skewness: -0.184944
      entropy: 0.915541
  Rendering intent: Perceptual
  Gamma: 0.454545
  Chromaticity:
    red primary: (0.64,0.33)
    green primary: (0.3,0.6)
    blue primary: (0.15,0.06)
    white point: (0.3127,0.329)
  Background color: white
  Border color: srgb(223,223,223)
  Matte color: grey74
  Transparent color: black
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 4624x3468+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  Quality: 92
  Orientation: RightTop
  Profiles:
    Profile-app4: 7600 bytes
    Profile-exif: 51509 bytes
  Properties:
    date:create: 2022-08-20T05:27:53+00:00
    date:modify: 2022-08-20T05:27:53+00:00
    exif:ApertureValue: 169/100
    exif:BrightnessValue: 264/100
    exif:ColorSpace: 1
    exif:DateTime: 2022:08:20 10:53:10
    exif:DateTimeDigitized: 2022:08:20 10:53:10
    exif:DateTimeOriginal: 2022:08:20 10:53:10
    exif:DigitalZoomRatio: 100/100
    exif:ExifOffset: 226
    exif:ExifVersion: 48, 50, 50, 48
    exif:ExposureMode: 0
    exif:ExposureProgram: 2
    exif:ExposureTime: 1/50
    exif:Flash: 0
    exif:FNumber: 180/100
    exif:FocalLength: 532/100
    exif:FocalLengthIn35mmFilm: 28
    exif:ImageLength: 3468
    exif:ImageUniqueID: I64ELODR0PM
    exif:ImageWidth: 4624
    exif:Make: samsung
    exif:MaxApertureValue: 169/100
    exif:MeteringMode: 2
    exif:Model: SM-M526B
    exif:OffsetTime: +05:30
    exif:OffsetTimeOriginal: +05:30
    exif:PhotographicSensitivity: 160
    exif:PixelXDimension: 4624
    exif:PixelYDimension: 3468
    exif:SceneCaptureType: 0
    exif:ShutterSpeedValue: 1/50
    exif:Software: M526BXXU1BVG4
    exif:thumbnail:Compression: 6
    exif:thumbnail:ImageLength: 384
    exif:thumbnail:ImageWidth: 512
    exif:thumbnail:JPEGInterchangeFormat: 782
    exif:thumbnail:JPEGInterchangeFormatLength: 50721
    exif:thumbnail:ResolutionUnit: 2
    exif:thumbnail:XResolution: 72/1
    exif:thumbnail:YResolution: 72/1
    exif:WhiteBalance: 0
    exif:YCbCrPositioning: 1
    jpeg:colorspace: 2
    jpeg:sampling-factor: 2x2,1x1,1x1
    signature: 7841c1e0cbe1aa5b79f0dea6791ffd321e2cf05715a9ab3cd210fd551c9bf355
  Artifacts:
    filename: shirish.jpg
    verbose: true
  Tainted: False
  Filesize: 3.65599MiB
  Number pixels: 16.036M
  Pixels per second: 126.41MB
  User time: 0.120u
  Elapsed time: 0:01.126
  Version: ImageMagick 6.9.11-60 Q16 x86_64 2021-01-25 https://imagemagick.org

现在，我尝试了imagemagick和jpegoptim来获得一个大约50k的文件。我需要这个大小的文件，因为我必须上传到某个地方，并有大小的禁忌。

我得到了上述exif和照片数据使用标识-verbose开关在imagemagick。

有人能帮我做上面的事吗。

我试过以下几点-

$jpegoptim --size=50k shirish.jpg

我得到的文件不是50 kb，而是200 kb，好但不是我想要的：

我甚至试过-

$jpegoptim --max=10 --size=50k shirish-aadhar-2-reduced.jpg

但即便如此，也没有产生预期的结果。

$ jpegoptim --version
jpegoptim v1.4.7  x86_64-pc-linux-gnu (Jun 20 2022)
Copyright (C) 1996-2022, Timo Kokkonen

This program comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistirbute it under certain conditions.
See the GNU General Public License for more details.


libjpeg version: 6b  27-Mar-1998
Copyright (C) 1991-2021 The libjpeg-turbo Project and many others

期待着帮助。我知道我可以用一些在线工具来做同样的事情，但是我想离线也是可能的。

Answer 1

您可以使用ImageMagick删除所有元数据并降低质量。有关更多信息，请访问这个答案：

在85个渐进式(压缩)中，一个非常微小的高斯模糊来优化尺寸(半径的0.05或0.5 )取决于图像的质量和大小，这明显地优化了jpeg的大小。删除图像中的任何注释或EXIF元数据应转换为-strip -interlace平面-模糊-quality 0.0 5 -quality 85% source.jpg result.jpg或更新版本: magick source.jpg -strip -interlace平面--quality 0.0 5-quality 85% result.jpg

你可以玩-quality号码。但是将16 so图像压缩到50k将不会产生那么好的效果。

Answer 2

如果格式为jpg，则可以定义最大文件大小：

convert shirish.jpg -define jpeg:extent=20k shirish-20k.jpg

这几乎肯定会大大降低你的形象质量。

但这是值得知道的。

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