PIL TIFF file size differing after reading and saving

Question

I have a tiff file that is 800kb in size (1pager), but when I read that tiff file with pil and save it again file size is reduced to 190KB. any reason why it happens??

from PIL import Image

path = tiff/file/path

img = Image.open(path)

img.save("test.tiff")

Answer 1

The most likely is that PIL has saved with a different compression scheme from your input file.

There are several tools you can use to check the content and compression of your files.

---

You could use exiftool like this:

exiftool a.tif

Sample Output

ExifTool Version Number         : 12.00
File Name                       : a.tif
Directory                       : .
File Size                       : 4.0 kB
File Modification Date/Time     : 2021:05:17 11:39:02+01:00
File Access Date/Time           : 2021:05:17 11:39:05+01:00
File Inode Change Date/Time     : 2021:05:17 11:39:02+01:00
File Permissions                : rw-r--r--
File Type                       : TIFF
File Type Extension             : tif
MIME Type                       : image/tiff
Exif Byte Order                 : Little-endian (Intel, II)
Image Width                     : 640
Image Height                    : 480
Bits Per Sample                 : 8 8 8
Compression                     : LZW          <--- CHECK COMPRESSION
Photometric Interpretation      : RGB
Fill Order                      : Normal
Strip Offsets                   : 8
Orientation                     : Horizontal (normal)
Samples Per Pixel               : 3
Rows Per Strip                  : 480
Strip Byte Counts               : 3837
Planar Configuration            : Chunky
Page Number                     : 0 1
Predictor                       : Horizontal differencing
White Point                     : 0.3127000032 0.328999996
Primary Chromaticities          : 0.6399999856 0.330000013 0.3000000118 0.6000000237 0.1500000058 0.05999999844
Image Size                      : 640x480
Megapixels                      : 0.307

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You could use tiffinfo which is shipped with libtiff like this:

tiffinfo a.tif

Sample Output

TIFF Directory at offset 0xf06 (3846)
  Image Width: 640 Image Length: 480
  Bits/Sample: 8
  Compression Scheme: LZW
  Photometric Interpretation: RGB color
  FillOrder: msb-to-lsb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 3
  Rows/Strip: 480
  Planar Configuration: single image plane
  Page Number: 0-1
  White Point: 0.3127-0.329
  PrimaryChromaticities: 0.640000,0.330000,0.300000,0.600000,0.150000,0.060000
  Predictor: horizontal differencing 2 (0x2) 

---

You could use ImageMagick like this:

magick identify -verbose a.tif

Sample Output

Image:
  Filename: a.tif
  Format: TIFF (Tagged Image File Format)
  Mime type: image/tiff
  Class: DirectClass
  Geometry: 640x480+0+0
  Units: PixelsPerInch
  Colorspace: sRGB
  Type: Palette
  Base type: TrueColor
  Endianness: LSB
  Depth: 8-bit
  Channel depth:
    Red: 8-bit
    Green: 1-bit
    Blue: 1-bit
  Channel statistics:
    Pixels: 307200
    Red:
      min: 0  (0)
      max: 255 (1)
      mean: 169.934 (0.666406)
      median: 127 (0.498039)
      standard deviation: 85.0846 (0.333665)
      kurtosis: -1.19989
      skewness: -0.500312
      entropy: 0.77808
    Green:
      min: 0  (0)
      max: 0 (0)
      mean: 0 (0)
      median: 0 (0)
      standard deviation: 0 (0)
      kurtosis: -3
      skewness: 0
      entropy: 0
    Blue:
      min: 0  (0)
      max: 0 (0)
      mean: 0 (0)
      median: 0 (0)
      standard deviation: 0 (0)
      kurtosis: -3
      skewness: 0
      entropy: 0
  Image statistics:
    Overall:
      min: 0  (0)
      max: 255 (1)
      mean: 56.6445 (0.222135)
      median: 42.3333 (0.166013)
      standard deviation: 28.3615 (0.111222)
      kurtosis: -0.0183471
      skewness: 1.30265
      entropy: 0.25936
  Colors: 256
  ...
  ...
  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)
  Matte color: grey74
  Background color: white
  Border color: srgb(223,223,223)
  Transparent color: none
  Interlace: None
  Intensity: Undefined
  Compose: Over
  Page geometry: 640x480+0+0
  Dispose: Undefined
  Iterations: 0
  Compression: LZW
  Orientation: TopLeft
  Convex hull: 0,0 639,0 639,478 638,479 1,479 0,478 0,0 
  Minimum bounding box: 639,0 639,479 0,479 0,0 
  Properties:
    date:create: 2021-05-17T10:39:02+00:00
    date:modify: 2021-05-17T10:39:02+00:00
    minimum-bounding-box:_p: 0,0
    minimum-bounding-box:_q: 639,0
    minimum-bounding-box:_v: 638,479
    minimum-bounding-box:angle: 0
    minimum-bounding-box:area: 306081
    minimum-bounding-box:height: 639
    minimum-bounding-box:unrotate: -0
    minimum-bounding-box:width: 479
    signature: 3987e368758bcc020b1c3bc26cc30a0aaf67aaeb38f31ac109b459fd8d25e708
    tiff:alpha: unspecified
    tiff:endian: lsb
    tiff:photometric: RGB
    tiff:rows-per-strip: 480
  Artifacts:
    verbose: true
  Tainted: False
  Filesize: 4114B
  Number pixels: 307200
  Pixels per second: 48.0479MP
  User time: 0.010u
  Elapsed time: 0:01.006
  Version: ImageMagick 7.0.10-48 Q16 x86_64 2020-12-10 https://imagemagick.org