vips tiffsave doesn't set predictor correctly

[Adios]

Bug report

Describe the bug

I try to re-compress an image in zip with --predictor set to horizontal as in

vips tiffsave GitHub-Mark.png vips_horizontal.tif --compression deflate --predictor horizontal

but it's seems to be ignored in the output image:

$ tiffinfo vips_horizontal.tif 
TIFF Directory at offset 0x3b3c (15164)
  Image Width: 560 Image Length: 560
  Resolution: 28.34, 28.34 pixels/cm
  Bits/Sample: 8
  Sample Format: unsigned integer
  Compression Scheme: AdobeDeflate
  Photometric Interpretation: RGB color
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 3
  Rows/Strip: 128
  Planar Configuration: single image plane

And no matter --predictor horizontal or --predictor none, they output the same file size, as if they were compressed without setting a predictor.

To Reproduce

Steps to reproduce the behavior:

1. use image: https://github.githubassets.com/images/modules/logos_page/GitHub-Mark.png
2. vips tiffsave GitHub-Mark.png vips_horizontal.tif --compression deflate --predictor horizontal
3. tiffinfo vips_horizontal.tif
4. vips tiffsave GitHub-Mark.png vips_none.tif --compression deflate --predictor none

Expected behavior

1. Should see Predictor: horizontal differencing 2 (0x2) in the tiffinfo output
2. vips_horizontal.tif & vips_none.tif should have different sizes (in most cases)

Actual behavior

1. No Predictor: horizontal differencing 2 (0x2) in the tiffinfo output
2. vips_horizontal.tif & vips_none.tif have the same size

Environment

• Linux 5.11.2-arch1-1

$ pacman -Q libtiff libvips imagemagick
libtiff 4.2.0-1
libvips 8.10.3-1
imagemagick 7.0.11.2-1

Additional context

As a comparison, use ImageMagick:

magick convert GitHub-Mark.png -compress zip -define tiff:predictor=2 gm_horizontal.tif

Could see the Predictor filed is set,

$ tiffinfo gm_horizontal.tif 
TIFF Directory at offset 0x2494 (9364)
  Image Width: 560 Image Length: 560
  Bits/Sample: 8
  Compression Scheme: AdobeDeflate
  Photometric Interpretation: palette color (RGB from colormap)
  FillOrder: msb-to-lsb
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 1
  Rows/Strip: 560
  Planar Configuration: single image plane
  Page Number: 0-1
  Color Map: (present)
  White Point: 0.3127-0.329
  PrimaryChromaticities: 0.640000,0.330000,0.300000,0.600000,0.150000,0.060000
  Predictor: horizontal differencing 2 (0x2)

And the generated image sizes are different: (with respect to -define tiff:predictor=1)

$ ls -l gm_horizontal.tif gm_none.tif 
-rw-r--r-- 1 adios adios 11174 Mar  4 04:18 gm_horizontal.tif
-rw-r--r-- 1 adios adios  9892 Mar  4 04:29 gm_none.tif

Additional context 2

I encountered this issue on Ubuntu (with homebrew) at beginning, and then I started a VM to install Arch to test and report the issue.

[jcupitt]

Hi @Adios, you're right, there was a mixup in enum values in the tiff saver which prevented it from setting the predictor correctly.

I now see:

$ vips tiffsave k2.jpg x.tif --compression deflate --predictor horizontal
$ tiffinfo x.tif
TIFF Directory at offset 0x38fa56 (3734102)
  Image Width: 1450 Image Length: 2048
  Resolution: 72.009, 72.009 pixels/inch
  Bits/Sample: 8
  Sample Format: unsigned integer
  Compression Scheme: AdobeDeflate
  Photometric Interpretation: RGB color
  Orientation: row 0 top, col 0 lhs
  Samples/Pixel: 3
  Rows/Strip: 128
  Planar Configuration: single image plane
  Predictor: horizontal differencing 2 (0x2)

This fix will be in 8.10.6, and I've credited you in the changelog.

Thank you very much for reporting this dumb thing!