Develop Reference

How can I do a compose in wand?

I'm trying to create a composition of an image with wand but I'm not able to find the right way to do so.
convert beijing_contrast.jpg beijing_blurmap.jpg \
-compose Blur -set option:compose:args 10 -composite \
beijing_model.jpg
Can anyone help me make this ImageMagick command with wand?

Try this.
with Image(filename='beijing_contrast.jpg') as src:
with Image(filename='beijing_blurmap.jpg') as dst:
src.composite(dst, operator='blur', arguments='10')
src.save(filename='beijing_model.jpg')
The method Image.composite() was updated in Python's Wand version 5.3 to include both operator= & arguments= parameters.

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.

Generate PDF from JPEGs in Separate Directories Grouped by Date/Name

I am looking to generate a PDF report from JPEGs on a server. The JPEGs are in folders named after the location they were taken and the JPEGs are named based on the date they were taken (...\Location 1\15 08 03 description.jpg). Basically I need to grab all pictures taken at each site last month, group them evenly on a page (4 max/page), label the pages with location and date, export PDF.
I have written projects in Powershell and Python so it would be a lot easier for me to operate in these languages but I will consider all suggestions.
So far, my idea is to use switch/case to select the various folder names, for loop through to select all cases, and select all files with .jpg extension within a month range (maybe user prompted?). Where I fall flat is arranging the JPEGs into a PDF as I described.
Edit: So if you follow Mark Setchell's advice below, create the images he suggested and place them in C:\New folder. So suppose you had in this sub directory 3 folders (New folder, New folder (2), etc.) and 2 of these contain the nine colored JPEGS and the third is empty:
clear
$path="C:\New folder\"
$array=#()
$name="file*.jpg"
foreach ($i in Get-ChildItem -path $path -Filter "New*")
{$i0=$path+$i; Get-ChildItem -path $i0 -Filter $name | ForEach-Object {$array+= $i0+"\"+$_.name}
montage $array -tile 2x2 -geometry +5+5 -title $i -page letter montage.pdf}`
My code overwrites the title on all pages with that of the 3rd empty folder. Also, it begins adding JPEGS from the next folder into the previous page, which should be titled as the previous folder and only contain those JPEGS.

Imagine you have 9 JPEG files in a directory, called file1.jpg...file9.jpg and they were created like this as lumps of red, green, blue, cyan, magenta, yellow, black and gray.
convert -size 300x400 xc:red file1.jpg
convert -size 300x400 xc:lime file2.jpg
convert -size 300x400 xc:blue file3.jpg
convert -size 300x400 xc:cyan file4.jpg
convert -size 300x400 xc:magenta file5.jpg
convert -size 300x400 xc:yellow file6.jpg
convert -size 300x400 xc:black file7.jpg
convert -size 300x400 xc:gray40 file8.jpg
convert -size 300x400 xc:gray80 file9.jpg
If you now go into that directory and run the following bash script, it will montage the files into pages of A4 with 4 images on each page.
#!/bin/bash
for f in file*jpg; do
convert -label "$f" "$f" -depth 8 miff:-
done | montage -tile 2x2 -geometry +5+5 miff:- -page A4 montage.pdf
The crux of the matter is firstly adding a label to each image based on the filename and secondly sending the label and the image to a MIFF file which is capable of holding many images. The combined group of images are then fed into montage whch arranges them four to a page because of the -tile 2x2. The geometry sets the spacing between the pictures - bigger numbers mean bigger spaces. Finally we tell montage that the paper size is A4 and we want a PDF of all the input images - please!
Of course you can diddle with the background, the sizing, the spacing and the labelling till you are happy - but this should give you the basic idea.
You will get out a PDF called montage.pdf with these three pages:
Page1
Page 2
Page 3
Its shoud be fairly trivial to convert the loop to an ugly Windows-y FOR loop - for loop help.

for converting your jpg's into pdf files you can use ImageMagick.
There are also different types of python APIs for imagemagick, but in your case is the best to write a simple powershell script and execute imagemagick directly.
Just use the following imagemagick command:
convert <yourfile.jpg> <newfile.pdf>
Note: You must use file extentions in your command. Otherwise imagemagick don't know what todo.

You could use glob to get the files (and then sort them if needed). I think the switch could get way too complicated.
As for the convert part: Shibumi's answer.

gdal_merge overlaying pngs over one another

I have a lot of PNGs that were tiled with gdal2tiles.py. I have done some processing on these tiles and now I would like combine them back into one large TIF.
For example I have folder 13-20 for different zoom levels, let's say I want all the PNGs from zoom level 20 to be a single mosaic, how would I do with gdal_merge? I'm using gdal_merge now trying this but I end up getting the last .PNG that it processes so my TIF is just a 256x256 TIF of the last processed PNG. Here is my current code,
python gdal_merge.py -o mos.tif -of GTiff -v --optfile tif_list.txt
tif_list.txt contains the list of all my PNGs
I'm assuming I might need to add a -co option but I cannot find any documentation on what I can use in -co. If this is needed my coordinate system is EPSG 3857, and the tiles were generated as mercator. Any help would be appreciated.
Update:
format of tif_list.txt,
C:\Users\Administrator\Desktop\19\195953\226590.png
C:\Users\Administrator\Desktop\19\195954\226581.png
C:\Users\Administrator\Desktop\19\195954\226582.png
C:\Users\Administrator\Desktop\19\195954\226583.png
C:\Users\Administrator\Desktop\19\195954\226584.png
C:\Users\Administrator\Desktop\19\195954\226585.png
C:\Users\Administrator\Desktop\19\195954\226586.png
C:\Users\Administrator\Desktop\19\195954\226587.png
C:\Users\Administrator\Desktop\19\195954\226588.png
C:\Users\Administrator\Desktop\19\195954\226589.png
C:\Users\Administrator\Desktop\19\195954\226590.png
C:\Users\Administrator\Desktop\19\195955\226581.png
C:\Users\Administrator\Desktop\19\195955\226582.png
C:\Users\Administrator\Desktop\19\195955\226583.png
C:\Users\Administrator\Desktop\19\195955\226584.png
C:\Users\Administrator\Desktop\19\195955\226585.png
C:\Users\Administrator\Desktop\19\195955\226586.png
C:\Users\Administrator\Desktop\19\195955\226587.png
C:\Users\Administrator\Desktop\19\195955\226588.png
C:\Users\Administrator\Desktop\19\195955\226589.png
C:\Users\Administrator\Desktop\19\195955\226590.png
examples of the PNGs,

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.