Develop Reference

Can I change the 'AppMag' or 'objective-power' attribute in a tif tile using tifftools (or any equivalent python library)?

I want to change the APPMag property in my tif file. The documentation provided by tifftools is not that clear. Can anyone help me with that.
I managed to change the APPMag by changing the Image Description like this:
tifftools set -y -s ImageDescription "secret phrase| AppMag = 100" photograph.tif
but this replaces the ImageDescription metadata. I only want to change the AppMag part. Can anyone please help me with that ?

Pillow script results in image losing saturation / vibrance

I have a Python script that uses Pillow to resize an image to an Instagram sized image with blurred background from the original image.
Before and after images (both JPGs):
https://app.box.com/s/jpv2mxlncp9871zvx9ygt0be4gf0zc9q
Is this simply a function of the 'after' JPG being too small to reflect all the colors in the original image? (Instagram only allows 2048x2048 images max, my original is a JPG converted from TIF from a 24.2-megapixel RAW image taken from a Nikon DSLR). Perhaps it's all in my head, but in my opinion, the 'after' image has lost some saturation / vibrance (compare the yellow buildings and car lights for example)
Has anyone experienced similar issues? Is there some default mode in Pillow that is reducing the number of colors available? I'm thinking of adding an additional saturation step to my script, but that seems like a hack.
EDIT: Added another before / after pair of images to the link above. I also realize I can easily share the script's source (GitHub repo):
https://github.com/princefishthrower/instagramize

The difference is that the original image contains an "ICC Colour Profile" (amongst others) which are not preserved in the output image.
You can see this most easily with exiftool:
exiftool Mountains_Before.jpg | grep -i profile
Or with ImageMagick:
magick identify -verbose Mountains_Before.jpg | grep -A999 Profiles:
Output
Profiles:
Profile-8bim: 92 bytes
Profile-exif: 17796 bytes
Profile-icc: 560 bytes
Profile-iptc: 80 bytes
City[1,90]: 0x00000000: 254700 -%G
Created Date[2,55]: 2020-7-1
unknown[2,62]: 2020-06-30
unknown[2,63]: 21:11:26+00:00
unknown[2,0]: 4
Created Time[2,60]: 20:22:05-20:22
Profile-xmp: 9701 bytes
If you strip the profiles from the original, you will see it too, is washed out and flatter:
magick Mountains_Before.jpg -strip NoProfile.jpg
You can extract the ICC Profile and look at out like this if that sort of thing excites you:
magick Mountains_Before.jpg profile.icc
If you did that, I guess you could re-attach the profile from the BEFORE image to the AFTER image like this:
magick Mountains_After.jpg -profile profile.icc AfterWithProfile.jpg
Keywords: Image processing, ImageMagick, profile, ICC profile, saturation, saturated, desaturated, washed out.

As Mark Setchell pointed out, it is a matter of preserving the color profile of the image, which is possible natively in Pillow, first by retrieving the profile after opening the image:
image = Image.open('mycoolimage.jpg')
iccProfile = image.info.get('icc_profile')
iccBytes = io.BytesIO(iccProfile)
originalColorProfile = ImageCms.ImageCmsProfile(iccBytes)
and when calling save with Pillow you can pass an icc_profile:
image.save('outputimagename.jpg', icc_profile=originalColorProfile.tobytes())
(Obviously, I am doing other manipulations to image in between these two steps here. Apparently one or more of them cause the icc_profile to disappear.)
This answer was also helpful in building this solution.
I added Mountains_After_NEW.jpg for those interested to see the results of these additions.

Sliced tiff image gets bigger with python Wand

I have a .tif file that has 10 pages. I want to create a sub-image containing only pages 2-7, but the produced file is much bigger than the orginal. It should be smaller. What would you suggest? Here is my code:
from wand.image import Image
with Image(filename='test.tif') as original:
with Image() as sub_image:
sub_image.sequence.extend(original.sequence[2:7])
sub_image.save(filename='sub.tif')
Original: 3mb
Sub: 50mb (!)
EDIT: Here a sample source file : tif file

There's a lot at play in the TIFF file. Try the following in the command line.
convert 'test.tif[2-7]' \
-define 'tiff:rows-per-strip=3504' \
-colorspace YCBCR \
-alpha remove \
-auto-level \
-compress JPEG \
-endian LSB \
-depth 8 \
output.tif
All options above match the original file except rows-per-strip. The original document has rows-per-strip of 3507; which is not a multiple of 8 (don't know what impact that would have).
The majority of the options are supported by wand, and should be implemented / respected in your calling script.
For -define 'tiff:rows-per-strip=3504', see this answer.

Stitch images together from html

This website has a large image combrised of 132 images, I want to find a way to stitch them together into a single image. I know some python if anyone has a clue where to start.
http://www.mapytatr.net/PRODUKTY/MAPY_TAT/WYSOKIE/SLICES/wys_ii.htm
Thanks!
Matt

Forget Python - use ImageMagic (http://www.imagemagick.org/)
+append to create row
convert tpn_1.jpg tpn_2.jpg tpn_3.jpg +append row_1.jpg
-append to create column
convert row_1.jpg row_2.jpg row_3.jpg -append final.jpg
You can try also montage (from ImageMagic too) to get all in one command
montage -mode concatenate -tile 3x3 tpn_* final.jpg
BTW: on Linux you can download all images using wget and for in bash
for i in $(seq 132); do echo "http://www.mapytatr.net/PRODUKTY/MAPY_TAT/WYSOKIE/SLICES/tpn_$i.jpg"; done | wget -i -
kochane tatry :)

Get a preview JPEG of a PDF on Windows?

I have a cross-platform (Python) application which needs to generate a JPEG preview of the first page of a PDF.
On the Mac I am spawning sips. Is there something similarly simple I can do on Windows?

ImageMagick delegates the PDF->bitmap conversion to GhostScript anyway, so here's a command you can use (it's based on the actual command listed by the ps:alpha delegate in ImageMagick, just adjusted to use JPEG as output):
gs -q -dQUIET -dPARANOIDSAFER -dBATCH -dNOPAUSE -dNOPROMPT \
-dMaxBitmap=500000000 -dLastPage=1 -dAlignToPixels=0 -dGridFitTT=0 \
-sDEVICE=jpeg -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -r72x72 \
-sOutputFile=$OUTPUT -f$INPUT
where $OUTPUT and $INPUT are the output and input filenames. Adjust the 72x72 to whatever resolution you need. (Obviously, strip out the backslashes if you're writing out the whole command as one line.)
This is good for two reasons:
You don't need to have ImageMagick installed anymore. Not that I have anything against ImageMagick (I love it to bits), but I believe in simple solutions.
ImageMagick does a two-step conversion. First PDF->PPM, then PPM->JPEG. This way, the conversion is one-step.
Other things to consider: with the files I've tested, PNG compresses better than JPEG. If you want to use PNG, change the -sDEVICE=jpeg to -sDEVICE=png16m.

You can use ImageMagick's convert utility for this, see some examples in http://studio.imagemagick.org/pipermail/magick-users/2002-May/002636.html
:
Convert taxes.pdf taxes.jpg
Will convert a two page PDF file into [2] jpeg files: taxes.jpg.0,
taxes.jpg.1
I can also convert these JPEGS to a thumbnail as follows:
convert -size 120x120 taxes.jpg.0 -geometry 120x120 +profile '*' thumbnail.jpg
I can even convert the PDF directly to a jpeg thumbnail as follows:
convert -size 120x120 taxes.pdf -geometry 120x120 +profile '*' thumbnail.jpg
This will result in a thumbnail.jpg.0 and thumbnail.jpg.1 for the two
pages.

Is the PC likely to have Acrobat installed? I think Acrobat installs a shell extension so previews of the first page of a PDF document appear in Windows Explorer's thumbnail view. You can get thumbnails yourself via the IExtractImage COM API, which you'll need to wrap. VBAccelerator has an example in C# that you could port to Python.