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Image Manipulation in Linux and Mac

Convert an image to WebP format

Install webp utility using Linux package manager or Homebrew in Mac.

cwebp -q quality (optional) input-image.jpg -o output-image.webp

# where quality is between 0 (poor) to 100 (very good).
# Typical value is around 80.

Convert a jpg to webp using image magick while resizing the image to 1200px and reducing the quality to 80%. The command below will resize and convert all the .jpg files in a given folder to their corresponding webp formats.

Note: the command below requires imagemagick version >= 7 

magick mogrify -resize 1200x -quality 80 -format webp *.jpg

Convert an SVG to PNG format

Using convert function from ImageMagick

# 300 dpi and 100% quality
convert -density 300 input.svg -quality 100 output.png

Density (-density)

  • Definition: The -density option specifies the resolution of the output image in dots per inch (DPI). It affects how the image is rendered, particularly for vector formats like SVG.
  • Usage: When you set -density 300, you are telling ImageMagick to render the SVG at a resolution of 300 DPI. This is particularly important for print quality, as higher DPI values result in more detail and sharper images.
  • Impact: A higher density value will generally produce a larger file size and better quality image, while a lower value may result in a smaller file size but lower quality.

Quality (-quality)

  • Definition: The -quality option specifies the compression level for the output image, particularly for formats like JPEG and PNG. It is a value between 0 and 100.
  • Usage: When you set -quality 100, you are indicating that you want the highest quality output. For PNG files, this means lossless compression, preserving all the image data.
  • Impact: A higher quality value results in better image fidelity but may increase the file size. Conversely, a lower quality value can reduce the file size but may introduce artifacts or reduce detail in the image.