Imagemagick转换工具为较小的几何体生成更大的文件大小?

时间:2010-10-22 03:22:57

标签: imagemagick

我尝试使用imagemagick 6.5.6的转换来从文件大小和几何中创建原始JPEG文件的较小版本。我使用的命令是:

convert tj/p1.jpg -resize 500x tj/456c2e75fe0faa57fd1cfd87117e0963/p1.jpg

结果很有趣,原版是164kb的1102x1542 + 0 + 0,转换的是174kb的500x700 + 0 + 0。像素数几乎是原始版本的20%,文件大小要大得多。所以我添加-strip选项来删除JPEG配置文件中的所有详细信息。

convert tj/p1.jpg -strip -resize 500x tj/500_p1.jpg

500_p1.jpg在173kb时为500x700 + 0 + 0,仅减少1kb。

我也尝试使用-thumbnail。

convert tj/p1.jpg -thumbnail 500x tj/th/p1.jpg

翻译的jpeg也是173kb的500x700 + 0 + 0。

最后我发现-quality可以帮助减少图像。但75%的质量需要107kb,25%的质量只需50kb,可见的细节损失。但原始品质因素尚不清楚。

有没有人有类似的问题?以下是通过识别生成的图像配置文件。我发现主要差异如下:

Geometry: 1102x1542->500x700
print size: 11x15->5x7
Units: Undefined->PixelsPerInch
Quality: unknown->92
Nr. of Pixels: 1.621mb->342kb

个人资料详情:

原件:

Image: tj/p1.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Class: DirectClass
  Geometry: 1102x1542+0+0
  Resolution: 100x100
  Print size: 11.02x15.42
  Units: Undefined
  Type: TrueColor
  Endianess: Undefined
  Colorspace: RGB
  Depth: 8-bit
  Channel depth:
    red: 8-bit
    green: 8-bit
    blue: 8-bit
  Channel statistics:
    red:
      min: 0 (0)
      max: 255 (1)
      mean: 218.106 (0.855319)
      standard deviation: 52.7336 (0.206798)
      kurtosis: 5.04278
      skewness: -2.24455
    green:
      min: 0 (0)
      max: 255 (1)
      mean: 158.476 (0.621473)
      standard deviation: 92.9844 (0.364645)
      kurtosis: -1.24112
      skewness: -0.535292
    blue:
      min: 0 (0)
      max: 255 (1)
      mean: 113.282 (0.444244)
      standard deviation: 99.7003 (0.390981)
      kurtosis: -1.59582
      skewness: 0.278377
  Image statistics:
    Overall:
      min: 0 (0)
      max: 255 (1)
      mean: 122.466 (0.480259)
      standard deviation: 108.274 (0.424604)
      kurtosis: -1.78198
      skewness: 0.0115088
  Rendering intent: Undefined
  Interlace: None
  Background color: white
  Border color: rgb(223,223,223)
  Matte color: grey74
  Transparent color: black
  Page geometry: 1102x1542+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  Orientation: Undefined
  Properties:
    date:create: 2010-10-22T08:35:35+08:00
    date:modify: 2010-09-30T10:52:06+08:00
    jpeg:colorspace: 2
    jpeg:sampling-factor: 2x2,1x1,1x1
    signature: cdbd3f63986f0a7c4cd20aedcf9123d91df97e0cb7388f59059b4676fd36d481
  Profiles:
    Profile-APP12: 15 bytes
  Artifacts:
    verbose: true
  Tainted: False
  Filesize: 164kb
  Number pixels: 1.621mb
  Pixels per second: 20.51mb
  User time: 0.078u
  Elapsed time: 0:01
  Version: ImageMagick 6.5.6-5 2009-09-25 Q16 OpenMP http://www.imagemagick.org

转换:

Image: tj/456c2e75fe0faa57fd1cfd87117e0963/p1.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Class: DirectClass
  Geometry: 500x700+0+0
  Resolution: 100x100
  Print size: 5x7
  Units: PixelsPerInch
  Type: TrueColor
  Endianess: Undefined
  Colorspace: RGB
  Depth: 8-bit
  Channel depth:
    red: 8-bit
    green: 8-bit
    blue: 8-bit
  Channel statistics:
    red:
      min: 0 (0)
      max: 255 (1)
      mean: 216.75 (0.849999)
      standard deviation: 50.1075 (0.1965)
      kurtosis: 4.066
      skewness: -2.03195
    green:
      min: 0 (0)
      max: 255 (1)
      mean: 158.316 (0.620846)
      standard deviation: 89.1433 (0.349582)
      kurtosis: -1.17694
      skewness: -0.52022
    blue:
      min: 0 (0)
      max: 255 (1)
      mean: 113.58 (0.445411)
      standard deviation: 96.3298 (0.377764)
      kurtosis: -1.53577
      skewness: 0.287937
  Image statistics:
    Overall:
      min: 0 (0)
      max: 255 (1)
      mean: 122.161 (0.479064)
      standard deviation: 106.052 (0.415889)
      kurtosis: -1.7498
      skewness: 0.00808184
  Rendering intent: Undefined
  Interlace: None
  Background color: white
  Border color: rgb(223,223,223)
  Matte color: grey74
  Transparent color: black
  Page geometry: 500x700+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  Quality: 92
  Orientation: Undefined
  Properties:
    date:create: 2010-10-22T10:27:18+08:00
    date:modify: 2010-10-22T10:31:08+08:00
    jpeg:colorspace: 2
    jpeg:sampling-factor: 2x2,1x1,1x1
    signature: 63202ddf9106d3374fe3a396f5105ce8099051cf807ceb2ab5a19532957cec10
  Artifacts:
    verbose: true
  Tainted: False
  Filesize: 174kb
  Number pixels: 342kb
  Version: ImageMagick 6.5.6-5 2009-09-25 Q16 OpenMP http://www.imagemagick.org

0 个答案:

没有答案