Pixeli is a lightweight and flexible command-line tool for merging multiple images into clean, customizable grid layouts. It’s designed for speed and simplicity, making it ideal for generating collages, previews, gallery layouts, inspiration boards, and composite images without relying on heavy desktop software.

Pixeli uses Sharp, a Node.js wrapper for the libvips library which is based on C. This makes it an extremely fast tool with support for PNG, JPG, GIF, SVG, AVIF, etc.

The tool currently supports two main layout modes: Grid and Masonry (horizontal / vertical). Each of them provide a distinct visual style to match a project's needs, for example:

Grid (1:1 images)	Contact Sheet Grid
Masonry (Horizontal)	Masonry (Vertical)
Collage (Instagram Grid)	Collage (Vertical Book Spread)
Collage (Horizontal Book Spread)	Collage (Dashboard Shot)
Collage (Art Gallery)

Pixeli can be installed using npm. Simply run the following command to install it globally on your machine:

npm i -g pixeli

You can also run pixeli directly with npx without installing it globally. This is convenient for quick experiments or one-off usage:

npx pixeli merge subcommand>gt; [options] files...>gt;

To run these examples, you can visit the GitHub Repository and use the images in the Samples directory, if you don't already have your own set of images.

All merge commands are under the pixeli merge command and can be used like so: pixeli merge [merge-mode] [options]

To create a basic grid with 1:1 images, you can use the grid merge command. You'll also need to provide the individual filepaths to use, or use the -rd (--recursive and --directory) flags to get all the images from the specified directory:

pixeli merge grid -rd ./samples/images

Without the -r flag, only the images in the directory will be scanned, and any sub-directories will be ignored.

To create a grid with images that all have the same aspect ratio, you can specify the aspect ratio to use for all images using the --ar flag:

pixeli merge grid -rd ./samples/images --ar 16:9

You can also customize the number of columns that you'd like the final image to have using the -c flag, followed by the number of columns:

pixeli merge grid -rd ./samples/images -c 8

Contact sheet style grids can also be made using pixeli. To include each file name under its respective image, the --ca flag can be used:

pixeli merge grid -rd ./samples/images --ca

The caption color can also be specified using the --cc flag, followed by a hex color:

pixeli merge grid -rd ./samples/images --ca --cc "#ff0000"

To create a masonry style image, you can use the masonry merge command. The -rd flag is used to specify which directory to use, and the canvas width can be specified using the --cvw flag:

pixeli merge masonry -rd ./samples/images --cvw 4000

By default, the masonry merge command uses a horizontal flow, but a vertical one can be specified using the -f flag, followed by the --cvh to specify the canvas height:

pixeli merge masonry -rd ./samples/images -f vertical --cvh 4000

Collage layouts require a JSON template, or an inline JSON string, which describe your specific layout. The -t flag is used to specify the path to a JSON template, whereas the -m flag is used to provide inline JSON:

pixeli merge collage -rd ./samples/images -t ./template.json

You could also use a preset, and also round all the image corners in your collage:

pixeli merge collage -rd ./samples/images -t ./template.json --cr 100

To learn about the JSON template, see collage templates.

Usage: pixeli merge [options] -o

-o <output>

The merge command is what allows you to create grids and mosaics with your images.

The following options and flags are shared for all of the subcommands under the pixeli merge command:

Usage: pixeli merge grid [options] [files...]

The grid mode arranges images into a clean, uniform grid with fixed columns and automatic row calculation. The table below displays all of the options available to this command:

Usage: pixeli merge masonry [options] [files...]

The masonry mode preserves each image’s natural shape, creating an organic brick-wall layout similar to Pinterest boards.

Usage: pixeli merge collage [options] [files...]

The collage merge requires a specified JSON template file, or JSON string. Images will be placed as per the template. If a preset ID is provided, both --template and --mapping are ignored.

The following javascript object thoroughly describes the shape of the JSON objects which are expected to be received. Logical checks are performed on the values after the template is validated. This is to ensure the collage can be created, for example, without any overlaps or 0 pixel-wide images:

{
   type: 'object',
   required: ['canvas', 'slots'],
   properties: {
     canvas: {
       type: 'object',
       required: ['width', 'height', 'columns', 'rows'],
       properties: {
         width: { type: 'number', minimum: 1, multipleOf: 1 },
         height: { type: 'number', minimum: 1, multipleOf: 1 },
         columns: { type: 'number', minimum: 1, multipleOf: 1 },
         rows: { type: 'number', minimum: 1, multipleOf: 1 },
         gap: { type: 'number', minimum: 0, multipleOf: 1 },
         background: { type: 'string' },
       },
     },

      slots: {
       type: 'array',
       items: {
         type: 'object',
         required: ['col', 'row', 'colSpan', 'rowSpan'],
         properties: {
           col: { type: 'number', minimum: 1, multipleOf: 1 },
           row: { type: 'number', minimum: 1, multipleOf: 1 },
           colSpan: { type: 'number', minimum: 1, multipleOf: 1 },
           rowSpan: { type: 'number', minimum: 1, multipleOf: 1 },
         },
       },
     },
   },

}

The template.canvas object defines key properties of the canvas, and the template.slots array lists all the slots in which images are to be placed.

A slot object takes 4 properties: col, row, colSpan, and rowSpan. col and row specify which column and row to place the image in, while colSpan and rowSpan define how many units the image should take up horizontally and vertically.

The width of a single unit is equal to canvas width divided by the number of columns, and the height of a single unit is equal to the canvas height divided by the number of rows.

For example:

{ 
   "col": 1,
   "row": 5,
   "colSpan": 3,
   "rowSpan": 2
}}

This slot will be placed at the 1st column from the left, at the 5th row from the top. It will span 3 columns, including the one it has been placed in, meaning it will take up column 1, 2, and 3. The same goes for the rows; the slot will take up row 5 and 6.

This is an example of a full JSON template:

{
   "canvas": {
     "width": 1200,
     "height": 1600,
     "columns": 3,
     "rows": 6,
     "gap": 12,
     "background": "#000"
  },
    "slots": [
    {  "col": 1, "row": 1, "colSpan": 2, "rowSpan": 2 },
    {  "col": 3, "row": 1, "colSpan": 1, "rowSpan": 1 },
    {  "col": 3, "row": 2, "colSpan": 1, "rowSpan": 1 },
    {  "col": 1, "row": 3, "colSpan": 1, "rowSpan": 2 },
    {  "col": 2, "row": 3, "colSpan": 2, "rowSpan": 2 },
    {  "col": 1, "row": 5, "colSpan": 3, "rowSpan": 2 }
  ]
}
}

Note that the canvas.background and canvas.gap properties are optional. If they are not provided, the defaults from the CLI options will be used. If both the CLI and template options exists, the template options take priority.

This project is licensed under the MIT License.

This project was submitted to Hack Club, a group consisting of over 100,000 teen hackers from around the world who work on cool projects and get to participate in awesome programs like Midnight.