Scale Down Bitmaps

• Parameters
• Usage
• Examples
• Known Bugs

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Scales down one or more bitmaps proportionally to match specific widths, in pixels, using ImageMagick.

Suitable for generating images to be used with srcset and sizes.

Each resized file will have its new width appended to the original file name, for example, when reducing "cat.jpg" to 600px, the new file name will be "cat-600.jpg".

Non-bitmap files passed to the script will be ignored.

Warning: globs are not accepted as parameters. If passed, they will cause the script to behave unexpectedly.

Parameters

Name	Type	Description	Default value
s	folder or file	The source folder or file.	The current folder.
d	folder	The destination folder.	A folder named "resized" in the current folder.
w	string	The widths to resize the bitmaps to, separated by spaces.	"400 700 900 1100 1400 1700 2000 2300 2700"

Usage

1. Install ImageMagick on your computer. You can follow these steps or, if you are on a Mac, use Homebrew.

$ brew install imagemagick

2. Clone or download Scale Down Bitmaps from the GitHub repository.

3. Extract and save the file scale-down.sh to your project root.

4. Make sure the file is executable by running the following command.

$ chmod +x ./scale-down.sh

5. Start scaling down bitmaps!

Examples

Process all bitmaps in the current folder with the default settings and save the results to ./resized.

$ ./scale-down.sh

Process all bitmaps in ./bitmaps with the default settings and save the results to ./bitmaps/resized.

$ ./scale-down.sh -s ./bitmaps

Process the file ./bitmaps/cat.jpg with the default settings and save the results to ./bitmaps/resized.

$ ./scale-down.sh -s ./bitmaps/cat.jpg

Process all bitmaps in ./bitmaps with the default settings and save the results to ./output.

$ ./scale-down.sh -s ./bitmaps -d ./output

Process all bitmaps in ./bitmaps with the widths passed as parameter and save the results to ./bitmaps/resized.

$ ./scale-down.sh -s ./bitmaps -w "400 800 1200"

Process all bitmaps in ./bitmaps with the widths passed as parameter and save the results to./output.

$ ./scale-down.sh -s ./bitmaps -d ./output -w "400 800 1200"

Process all bitmaps in the current folder with the widths passed as parameter and save the results to ./resized.

$ ./scale-down.sh -w "400 800 1200 1600"

Known Bugs

Image size verification will fail on animated gif images, causing the script to scale up this format.