Auto-cropping

ImageMagick can automatically crop surrounding transparent pixels from an image:

convert input.png -trim +repage output.png

You need to +repage to update the image's canvas, or applications will be randomly confused.
Trim...

ImageMagick takes a string with several options when cropping an image. See the command line options for how to provide the expected image geometry for details.

Note that I...

When you write your next CarrierWave uploader, consider processing your images with libvips instead of ImageMagick.

Reasons for libvips

There are several **upsi...

I recently noticed a new kind of flaky tests on the slow free tier GitHub Action runners: Integration tests were running on smaller screen sizes than [specified in the device metrics](https://makandracards.com/makandra/492109-capybara-running-test...

Debugging image color profiles is hard. You can't trust your eyes in this matter, as the image rendering depends on multiple factors. At least the operation system, browser or image viewer software and monitor influence the resulting image colors ...

Conversion

ImageMagick can convert SVGs to raster image formats.

Example for PNG:

convert input.svg output.png

If the SVG has a size of 24x24 (viewBox="0 0 24 24"), the resulting PNG will also have a size of 24x24.

Resizing...

Trick: Do not use convert but mogrify:

mogrify -resize 50% *

This overwrites the original image file.

In contrast, convert writes to a different image file. Here is an example if you need this:

cd /path/to/image/directory

...

Carrierwave includes some handy helper methods you can use to resize your images. Here is a quick summary of them, if you need more details read the [docs](https://github.com/carrierwaveuploader/carrierwave/blob/ff0ffc06f902aa92b30ad6a40d3624511e4...

Applications often show or hide elements based on viewport dimensions, or may have components that behave differently (like mobile vs desktop navigation menus).
Since you want your integration tests to behave consistently, you want to set a specif...

When you need test images, instead of using services like lorempixel or placehold.it you may generate test images yourself.

Here we build a simple SVG image and wrap it into a data: URI. Al...