Fear not Blender fans – Nicholas will return next month. Well, assuming his employer will actually give him a day off and some free time that is…
It's a common enough task, trying to convert multiple jpg files into one pdf, particularly when I don't need these to be converted with such high quality, I just want the black and white text readable.
I can scan, crop, and monochrome in a graphics program, but compiling them into a single PDF booklet was always tricky. Which is how I started using ImageMagick.
ImageMagick is a command-line conversion program that is capable of so many more batch operations than this - resizing, compression, format conversion - and it's available on all platforms - Linux, Windows and Mac.
Bear in mind that creating a PDF document from multiple JPEG images can take some time, and you may want to trial different settings for size and quality of output, so I suggest you make a copy of the JPEG files in a temporary folder to play around with and use Imagemagick on those – NOT on your originals. Reducing the resolution as a first step will also make things much quicker.
Originally I was just using the basic:
convert *.jpg output.pdf and/or convert *.jpg -adjoin output.pdf
which works most of the time. However, there's a bug in the convert routine which can in some versions give a segmentation fault when converting a number of JPEG files to one PDF file.
What this command does is take all the .jpg's (or format of your choice) in a folder, and convert them to a single PDF - you can name it whatever you like.
You can avoid the segmentation fault bug and do the compression at the same time if you use: convert *.JPG -compress Zip output.pdf
but the zip compression appears quite inefficient and results in huge file sizes.
You could resize and lower the quality of the images using:
mogrify -resize 50% -quality 25
Which overwrites the originals. You can combine resizing and conversion using:
convert -quality 25 -resize 50% *.jpg -adjoin output.pdf
which works, but takes longer as you're combining batch operations.
And yes, you can resizing images without overwriting the originals by specifying a new file name:
convert '*.JPG' -resize 640×480 newfile%03d.jpg
which outputs the converted images as newfile001.jpg, newfile002.jpg, and so on. Alternatively, if you want to retain the original filename and prepend “new”, you could use a bit more code:
for file in *.JPG ; do convert “$file” -resize 640×480 “new-${file}” ; done
This is just a sample of what Imagemagick can do if you are prepared to experiment at the command-line.