Is it possible to change an image resolution expressed in pixels per inch (PPI) in batch mode, using command line?

My images resolution is currently below 100 PPI.
I would like to enhance it to 300 PPI.
I am preparing a document for self publish.
The agency says that the images PPI should be 300.

1 Answer

Hello and welcome to Ubuntu.SE!

Here is a proposal using ImageMagick

You can use ImageMagick for that task:

Example

Here is a 40x30 pixels original image (file size of 1367 bytes) with a resolution of 72 PPI (in both X and Y directions):

You can change its resolution using the following command:

convert -units PixelsPerInch my_original_image.jpg -density 300 my_new_image.jpg

This is the result of the previous command:

X Resolution 300 PPI
Y Resolution 300 PPI
Image Size 40x30 pixels
File Size 981 bytes

Or if you need resampling:

convert -units PixelsPerInch my_original_image.jpg -resample 300 my_new_image.jpg

Which gives:

X Resolution 300 PPI
Y Resolution 300 PPI
Image Size 167x125 px
File Size 7.7 kB

Don't hesitate to open these images with Gimp for example to see the differences.

Source

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