Last time I used convert
for such a task I explicitly specified the size of the destination via resizing:
$ i=150; convert a.png b.png -compress jpeg -quality 70 \
-density ${i}x${i} -units PixelsPerInch \
-resize $((i*827/100))x$((i*1169/100)) \
-repage $((i*827/100))x$((i*1169/100)) multipage.pdf
The convert
command doesn't always use DPI as default density/page format unit, thus we explicitly specify DPI with the -units
option (otherwise you may get different results with different versions/input format combinations). The new size (specified via -resize
) is the dimension of a DIN A4 page in pixels. The resize argument specifies the maximal page size. What resolution and quality to pick exactly depends on the use case - I selected 150 DPI and average quality to save some space while it doesn't look too bad when printed on paper.
Note that convert
by default does not change the aspect ratio with the resize operation:
Resize will fit the image into the requested size.
It does NOT fill, the requested box size.
(ImageMagick manual)
Depending on the ImageMagick version and the involved input formats it might be ok to omit the -repage
option. But sometimes it is required and without that option the PDF header might contain too small dimensions. In any case, the -repage
shouldn't hurt.
The computations use integer arithmetic since bash
only supports that. With zsh
the expressions can be simplified - i.e. replaced with $((i*8.27))x$((i*11.69))
.
Lineart Images
If the PNG files are bi-level (black & white a.k.a lineart) images then the img2pdf
tool yields superior results over ImageMagick convert
. That means img2pdf
is faster and yields smaller PDFs.
Example:
$ img2pdf -o multipage.pdf a.png b.png
or:
$ img2pdf --pagesize A4 -o multipage.pdf a.png b.png
I assume you want to add a border of, say 30px, on all four sides. Use the -border
option for the size and -bordercolor
for the colour:
convert -border 30 -bordercolor white input.png output.pdf
More information can be found here: Imagemagick - Adding/Removing Image Edges
If you want the final PDF to be of a particular size, you can use the following options:
convert \
-page A4 \
-gravity northwest \
-border 30 \
-bordercolor white \
input.png output.pdf
Best Answer
Requirements
ImageMagick
Type the follow line to commmand prompt for intall ImageMagick:
Convert from jpegs to PDF:
Go to the work directory (directory of jpegs):
Convert the JPG files to PDF:
source : http://bitprison.net/jpg_to_pdf