Grunt Image Compiler

Grunt Image Compiler for Image Optimization using GraphicsMagick. Running this script will optimize images in set folder. First operation images will first be compressed, optimized, resized and then saved with the set naming convention. Second operation images will be saved to web format and stored in same output directory. HTML and CSS Examples on how to setup images, breakpoints and fallback images.

Install Dependancies

GraphicsMagick brew install graphicsmagick
Grunt CLI npm install -g grunt-cli
Run NPM npm install or Yarn yarn install

Run

To run the Grunt Task Runner operations type grunt in the cli.

Image Breakpoints

Small - sm

1x | quality: 60% | width: 600px
2x | quality: 60% | width: 1200px

Medium - md

1x | quality: 60% | width: 900px
2x | quality: 60% | width: 1800px

Large - lg

1x | quality: 60% | width: 1440px
2x | quality: 60% | width: 2880px

Image settings can be adjusted in Gruntfile.js

1x and 2x Explained

1x and 2x represent pixel density for device screen widths. Screen resolutions have hardware pixels and software pixels. Hardware pixels are no longer equal to the software or CSS pixel with newer displays. The relationship between hardware and CSS pixels are described by the following formula: CSS Pixels = Hardware Pixels / Pixel density Therefore, hardware resolution of 2880px translates to 1440px CSS pixels on the retina display.

Naming convention

Image names will be appended with the following attributes

Original filename: example-image.jpg
Compiled output filenames; example-image-sm_1x.jpg, example-image-sm_2x.jpg, example-image-md_1x.jpg, example-image-md_2x.jpg, example-image-lg_1x.jpg, example-image-lg_2x.jpg example-image-sm_1x.webp, example-image-sm_2x.webp, example-image-md_1x.webp, example-image-md_2x.webp, example-image-lg_1x.webp, example-image-lg_2x.webp

Default Fallback Images

To ensure proper cross-browser compatibily original source files should also be optimized and then always set as the default fallback image

Code Examples

HTML

<picture class="responsive-image">
    <source
        media="(min-width: 900px)"
        srcset="../dist/images/example-1-lg_1x.webp 1x, ../dist/images/example-1-lg_2x.webp 2x"
        type="image/webp" >
    <source
        media="(min-width: 601px)"
        srcset="../dist/images/example-1-md_1x.webp 1x, ../dist/images/example-1-md_2x.webp 2x"
        type="image/webp" >
    <source
        srcset="../dist/images/example-1-sm_1x.webp 1x, ../dist/images/example-1-sm_2x.webp 2x"
        type="image/webp" >
    <img 
        srcset="../dist/images/example-1-sm_1x.jpg 600w,
        ../dist/images/example-1-md_1x.jpg 900w,
        ../dist/images/example-1-lg_1x.jpg 1440w" 
        src="../dist/images/example-1-lg_1x.jpg"
        type="image/jpeg"
        alt="image description">
</picture>

SCSS

.bg-image {
  width: 100vw;
  height: 500px;
  background-size: cover;
  background-position: center;
  // large images (lg)
  background-image: url("../dist/images/example-1-lg_1x.jpg"); 
  background-image: -webkit-image-set(
    url("../dist/images/example-1-lg_1x.webp") 1x,
    url("../dist/images/example-1-lg_2x.webp") 2x
  );
  background-image: image-set(
    url("../dist/images/example-1-lg_1x.jpg") 1x,
    url("../dist/images/example-1-lg_2x.jpg") 2x
  );
  // medium images (md)
    @media(max-width: 900px) {
      background-image: url("../dist/images/example-1-md_1x.jpg");
      background-image: -webkit-image-set(
        url("../dist/images/example-1-md_1x.webp") 1x,
        url("../dist/images/example-1-md_2x.webp") 2x
      );
      background-image: image-set(
        url("../dist/images/example-1-md_1x.jpg") 1x,
        url("../dist/images/example-1-md_2x.jpg") 2x
      );
  }
  // small images (sm)
    @media (max-width: 600px) {
      background-image: url("../dist/images/example-1-sm_1x.jpg");
      background-image: -webkit-image-set(
        url("../dist/images/example-1-sm_1x.webp") 1x,
        url("../dist/images/example-1-sm_2x.webp") 2x
      );
      background-image: image-set(
        url("../dist/images/example-1-sm_1x.jpg") 1x,
        url("../dist/images/example-1-sm_2x.jpg") 2x
      );
    }
}

Credit to Maciej Nowakowski for his article that helped make this boilerplate.

License

MIT

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