JPEG compression for grayscale TIFF images does not work

[zanderoc]

When using JPEG compression inside a TIFF file format, grayscale images are unusually large, much larger than a color copy. This seems to be a BUG. We have used the following version of ImageMagick:

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Version: ImageMagick 6.6.1-4 2010-04-21 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

We have applied three conversion steps to the following three images:

• fractal.color.tif - original color image in uncompressed TIFF format
• fractal.gray.tif - derived grayscale image (from fractal.color.tif) in uncompressed TIFF format
• fractal.gray.one-red-pixel.tif - fractal.gray.tif converted to rgb color format with one red pixel embedded

Using these images, we have converted them to (1) JPEG, (2) TIFF with JPEG compression and (3) pyramidal TIFF with JPEG compression using these commands:

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(1) convert IMAGE.tif -quality 70 IMAGE.jpg
(2) convert IMAGE.tif -format tiff -compress jpeg -quality 70 IMAGE.jpg.tif
(3) convert IMAGE.tif -define tiff:tile-geometry=128x128 -format tiff -compress jpeg -quality 70 ptif:IMAGE.jpg.pyr.tif

The resulting file sizes are as follows (listing re-sorted with original image first):

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-rw-r--r-- 1 anybody users 2359676 2010-04-22 12:30 fractal.color.tif
-rw-r--r-- 1 anybody users   59847 2010-04-22 12:31 fractal.color.jpg
-rw-r--r-- 1 anybody users  165257 2010-04-22 12:34 fractal.color.jpg.tif
-rw-r--r-- 1 anybody users   69211 2010-04-22 12:35 fractal.color.jpg.pyr.tif

-rw-r--r-- 1 anybody users  786806 2010-04-22 12:30 fractal.gray.tif
-rw-r--r-- 1 anybody users   53652 2010-04-22 12:33 fractal.gray.jpg
-rw-r--r-- 1 anybody users  787530 2010-04-22 12:33 fractal.gray.jpg.tif
-rw-r--r-- 1 anybody users  264474 2010-04-22 12:35 fractal.gray.jpg.pyr.tif

-rw-r--r-- 1 anybody users 2359690 2010-04-22 12:39 fractal.gray.one-red-pixel.tif
-rw-r--r-- 1 anybody users   55539 2010-04-22 12:43 fractal.gray.one-red-pixel.jpg
-rw-r--r-- 1 anybody users  168901 2010-04-22 12:43 fractal.gray.one-red-pixel.jpg.tif
-rw-r--r-- 1 anybody users   71303 2010-04-22 12:44 fractal.gray.one-red-pixel.jpg.pyr.tif

While the grayscale image converts well to JPEG, with the JPEG compressed TIFF file, there is no compression visible. With the pyramidal TIFF images, we did not get the necessary JPEG compression when the source was a grayscale image either. For reporting this bug, we used an image with relatively small image dimensions (1024x768). Creating a pyramidal TIFF with these dimensions resulted in a corrupted image. Images with larger dimensions (>4k x 4k) were processed fine (except for the JPEG compression bug, which still appears with larger pyramidal JPEG compressed TIFF files). I will create a new thread for this image corruption bug.

[zanderoc]

No reply, yet? Anyone who can help?

Here is another example, that may demonstrate the issue better:

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-rw-r--r-- 1 anybody users 19621852 2010-04-26 12:52 4173699_00351.tif
-rw-r--r-- 1 anybody users 26705410 2010-04-26 13:19 4173699_00351.gray.jpg.pyr.tif
-rw-r--r-- 1 anybody users  8085488 2010-04-26 13:18 4173699_00351.color.jpg.pyr.tif

4173699_00351.tif is a grayscale uncompressed TIFF file (size 4844x4044 pixels). This has been converted to a pyramidal JPEG compressed image with the following two commands. Please note that after converting to RGB color and embedding one colored pixel, the image compresses as it should. In grayscale, it does not compress.

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convert 4173699_00351.tif -colorspace rgb -depth 8 -fill "#ff0000" -draw "point 1,1" -define tiff:tile-geometry=128x128 -format tiff -compress jpeg -quality 70 ptif:4173699_00351.color.jpg.pyr.tif
convert 4173699_00351.tif -define tiff:tile-geometry=128x128 -format tiff -compress jpeg -quality 70 ptif:4173699_00351.gray.jpg.pyr.tif

This behavior is not dependent on the pyramidal tiling of the image. The bug shows simply by compressing an image in JPEG and embedding this into a TIFF:

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convert 4173699_00351.tif -format TIFF -compress jpeg -quality 70 4173699_00351.gray.jpg.tif
convert 4173699_00351.tif -colorspace rgb -depth 8 -fill "#ff0000" -draw "point 1,1" -format tiff -compress jpeg -quality 70 4173699_00351.color.jpg.tif

This results in the following file sizes:

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-rw-r--r-- 1 anybody users 19621852 2010-04-26 12:52 4173699_00351.tif
-rw-r--r-- 1 anybody users 19621862 2010-04-26 13:26 4173699_00351.gray.jpg.tif
-rw-r--r-- 1 anybody users  5785757 2010-04-26 13:27 4173699_00351.color.jpg.tif

Again, the image with one colored pixel compresses really well, whereas the grayscale image does NOT compress.

[magick]

Apologies. We think the problem is fixed in ImageMagick 6.6.1-5, the current release. Download it and let us know if you have further problems.