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calibreapp
image-actions versus TinyPng
TinyPNG.com seems to produce much smaller images (40-60% smaller) with no noticeable loss in quality as far as my untrained eye can see. Any ideas how they do this? As I do really like this integration in GitHub Actions but at the moment I end up using this for the immediate effect and then going back and TinyPNG-ing the images later when I have time.
Any way to look at images and see what compression ratio they are using? Or are they stripping meta-data that Calibre is not? Or something else?
Would love it, it there was a simple config change to get same savings and save me this effort!
Thanks for the report @bazzadp, if you've got some file compression stats to share it may be helpful to figure out a target for us to reach.
To answer your questions:
Can we see what compression ratio they are using?
Nope. Though you can inspect the resulting files to explore their properties using the ImageMagick identify command:
identify -verbose public/slack-app-icon.png
Verbose command output
Image:
Filename: public/slack-app-icon.png
Format: PNG (Portable Network Graphics)
Mime type: image/png
Class: DirectClass
Geometry: 800x800+0+0
Resolution: 28.35x28.35
Print size: 28.2187x28.2187
Units: PixelsPerCentimeter
Colorspace: sRGB
Type: PaletteAlpha
Base type: Undefined
Endianness: Undefined
Depth: 8-bit
Channel depth:
Red: 8-bit
Green: 8-bit
Blue: 8-bit
Alpha: 8-bit
Channel statistics:
Pixels: 640000
Red:
min: 48 (0.188235)
max: 255 (1)
mean: 101.051 (0.396277)
standard deviation: 90.2672 (0.353989)
kurtosis: -0.751185
skewness: 1.11646
entropy: 0.167521
Green:
min: 87 (0.341176)
max: 255 (1)
mean: 130.056 (0.510023)
standard deviation: 73.2604 (0.287296)
kurtosis: -0.751204
skewness: 1.11645
entropy: 0.18027
Blue:
min: 244 (0.956863)
max: 255 (1)
mean: 246.819 (0.967917)
standard deviation: 4.79682 (0.0188111)
kurtosis: -0.751132
skewness: 1.11663
entropy: 0.237999
Alpha:
min: 253 (0.992157)
max: 255 (1)
mean: 254.998 (0.99999)
standard deviation: 0.0499688 (0.000195956)
kurtosis: 362.061
skewness: -19.9588
entropy: 0.0159103
Image statistics:
Overall:
min: 48 (0.188235)
max: 255 (1)
mean: 183.231 (0.718552)
standard deviation: 42.0936 (0.165073)
kurtosis: -1.58611
skewness: -0.5781
entropy: 0.150425
Colors: 52
Histogram:
473514: (48,87,244,255) #3057F4FF srgba(48,87,244,1)
1598: (48,87,244,254) #3057F4FE srgba(48,87,244,0.996078)
1: (48,87,244,253) #3057F4FD srgba(48,87,244,0.992157)
143: (61,98,245,255) #3D62F5FF srgba(61,98,245,1)
6: (73,108,245,255) #496CF5FF srgba(73,108,245,1)
208: (74,108,245,255) #4A6CF5FF srgba(74,108,245,1)
6: (75,108,245,255) #4B6CF5FF srgba(75,108,245,1)
5: (87,118,245,255) #5776F5FF srgba(87,118,245,1)
55: (87,118,246,255) #5776F6FF srgba(87,118,246,1)
1: (88,118,246,255) #5876F6FF srgba(88,118,246,1)
46: (99,129,246,255) #6381F6FF srgba(99,129,246,1)
74: (100,129,247,255) #6481F7FF srgba(100,129,247,1)
11: (112,139,247,255) #708BF7FF srgba(112,139,247,1)
9: (112,139,248,255) #708BF8FF srgba(112,139,248,1)
25: (113,139,248,255) #718BF8FF srgba(113,139,248,1)
61: (125,150,248,255) #7D96F8FF srgba(125,150,248,1)
56: (126,150,248,255) #7E96F8FF srgba(126,150,248,1)
41: (138,160,248,255) #8AA0F8FF srgba(138,160,248,1)
21: (138,161,248,255) #8AA1F8FF srgba(138,161,248,1)
5: (139,160,249,255) #8BA0F9FF srgba(139,160,249,1)
4: (139,161,249,255) #8BA1F9FF srgba(139,161,249,1)
128: (151,171,249,255) #97ABF9FF srgba(151,171,249,1)
33: (152,171,250,255) #98ABFAFF srgba(152,171,250,1)
11: (163,181,250,255) #A3B5FAFF srgba(163,181,250,1)
8: (163,182,250,255) #A3B6FAFF srgba(163,182,250,1)
37: (164,181,250,255) #A4B5FAFF srgba(164,181,250,1)
5: (164,181,251,255) #A4B5FBFF srgba(164,181,251,1)
13: (164,182,250,255) #A4B6FAFF srgba(164,182,250,1)
2: (164,182,251,255) #A4B6FBFF srgba(164,182,251,1)
1: (165,182,251,255) #A5B6FBFF srgba(165,182,251,1)
27: (176,191,251,255) #B0BFFBFF srgba(176,191,251,1)
83: (177,192,251,255) #B1C0FBFF srgba(177,192,251,1)
2: (178,192,251,255) #B2C0FBFF srgba(178,192,251,1)
10: (189,201,251,255) #BDC9FBFF srgba(189,201,251,1)
3: (189,202,251,255) #BDCAFBFF srgba(189,202,251,1)
24: (190,202,251,255) #BECAFBFF srgba(190,202,251,1)
7: (190,203,251,255) #BECBFBFF srgba(190,203,251,1)
48: (202,212,252,255) #CAD4FCFF srgba(202,212,252,1)
5: (202,213,252,255) #CAD5FCFF srgba(202,213,252,1)
97: (203,213,252,255) #CBD5FCFF srgba(203,213,252,1)
5: (215,222,253,255) #D7DEFDFF srgba(215,222,253,1)
8: (215,223,253,255) #D7DFFDFF srgba(215,223,253,1)
29: (216,223,253,255) #D8DFFDFF srgba(216,223,253,1)
72: (228,233,254,255) #E4E9FEFF srgba(228,233,254,1)
20: (228,234,254,255) #E4EAFEFF srgba(228,234,254,1)
127: (229,234,254,255) #E5EAFEFF srgba(229,234,254,1)
64: (241,243,254,255) #F1F3FEFF srgba(241,243,254,1)
2: (241,244,254,255) #F1F4FEFF srgba(241,244,254,1)
91: (242,244,254,255) #F2F4FEFF srgba(242,244,254,1)
43: (254,254,255,255) #FEFEFFFF srgba(254,254,255,1)
78: (254,255,255,255) #FEFFFFFF srgba(254,255,255,1)
163027: (255,255,255,255) #FFFFFFFF white
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)
Matte color: grey74
Background color: white
Border color: srgb(223,223,223)
Transparent color: none
Interlace: None
Intensity: Undefined
Compose: Over
Page geometry: 800x800+0+0
Dispose: Undefined
Iterations: 0
Compression: Zip
Orientation: Undefined
Convex hull: 0,0 799,0 799,798 798,799 0,799 0,0
Minimum bounding box: 799,0 799,799 0,799 0,0
Properties:
date:create: 2020-08-03T03:25:32+00:00
date:modify: 2020-06-18T02:59:15+00:00
minimum-bounding-box:_p: 0,0
minimum-bounding-box:_q: 799,0
minimum-bounding-box:_v: 798,799
minimum-bounding-box:angle: 0
minimum-bounding-box:area: 638401
minimum-bounding-box:height: 799
minimum-bounding-box:unrotate: -0
minimum-bounding-box:width: 799
png:IHDR.bit-depth-orig: 8
png:IHDR.bit_depth: 8
png:IHDR.color-type-orig: 6
png:IHDR.color_type: 6 (RGBA)
png:IHDR.interlace_method: 0 (Not interlaced)
png:IHDR.width,height: 800, 800
png:pHYs: x_res=2835, y_res=2835, units=1
png:sRGB: intent=0 (Perceptual Intent)
signature: e2875f86b03276de50966f8e48fb15ab8c84b97be74570d96d58b429fcc1522c
Artifacts:
verbose: true
Tainted: False
Filesize: 9229B
Number pixels: 640000
Pixels per second: 65.7632MP
User time: 0.020u
Elapsed time: 0:01.009
Version: ImageMagick 7.0.10-27 Q16 x86_64 2020-08-11 https://imagemagick.org
Maybe there's some clues there?
Or are they stripping meta-data that Calibre is not?
Internally image-actions uses sharp. The default configuration is to not include metadata. You'll find reference of this in the sharp docs:
The default behaviour, when
withMetadatais not used, is to convert to the device-independent sRGB colour space and strip all metadata, including the removal of any ICC profile.
AFAIK, the differences you've observed are not metadata related.
@bazzadp Once we've some details on the images themselves, we can start to explore the differences in output and take it from there.
Thanks @benschwarz !
Please find attached all the details
It looks to me like the histogram is about half the size - which is directly reflected in the file size.
I dunno if they just have a much more aggressive compression level, or if they use any magic to figure out what they can get away with in terms of compression level?