Merge several images into a single image

🤖/image/merge merges several images into a single spritesheet..

Using this Robot, it's possible to merge several images together into a single larger image.

The final result will be a sprite-sheet, with the images displayed horizontally or vertically

It's recommended to use this Robot with 🤖/image/resize so your images are of a similar size before merging them.

Parameters

use

String / Array of Strings / Objectrequired
Specifies which Step(s) to use as input.
- You can pick any names for Steps except ":original" (reserved for user uploads handled by Transloadit)
- You can provide several Steps as input with arrays:
```
"use": [
  ":original",
  "encoded",
  "resized"
]
```
💡 That’s likely all you need to know about use, but you can view advanced use cases:
› Advanced use cases
- Step bundling. Some Robots can gather several Step results for a single invocation. For example, 🤖/file/compress would normally create one archive for each file passed to it. If you'd set bundle_steps to true, however, it will create one archive containing all the result files from all Steps you give it. To enable bundling, provide an object like the one below to the use parameter:
```
"use": {
  "steps": [
    ":original",
    "encoded",
    "resized"
  ],
  "bundle_steps": true
}
```
  This is also a crucial parameter for 🤖/video/adaptive, otherwise you'll generate 1 playlist for each viewing quality.
  Keep in mind that all input Steps must be present in your Template. If one of them is missing (for instance it is rejected by a filter), no result is generated because the Robot waits indefinitely for all input Steps to be finished.
  
  Here’s a demo that showcases Step bundling.
- Group by original. Sticking with 🤖/file/compress example, you can set group_by_original to true, in order to create a separate archive for each of your uploaded or imported files, instead of creating one archive containing all originals (or one per resulting file). This is important for for 🤖/media/playlist where you'd typically set:
```
"use": {
  "steps": [
    "segmented"
  ],
  "bundle_steps": true,
  "group_by_original": true
}
```
- Fields. You can be more discriminatory by only using files that match a field name by setting the fields property. When this array is specified, the corresponding Step will only be executed for files submitted through one of the given field names, which correspond with the strings in the name attribute of the HTML file input field tag for instance. When using a back-end SDK, it corresponds with myFieldName1 in e.g.: $transloadit->addFile('myFieldName1', './chameleon.jpg').
  
  This parameter is set to true by default, meaning all fields are accepted.
  
  Example:
```
"use": {
  "steps": [ ":original" ],
  "fields": [ "myFieldName1" ]
}
```
- Use as. Sometimes Robots take several inputs. For instance, 🤖/video/merge can create a slideshow from audio and images. You can map different Steps to the appropriate inputs.
  
  Example:
```
"use": {
  "steps": [
    { "name": "audio_encoded", "as": "audio" },
    { "name": "images_resized", "as": "image" }
  ]
}
```
  Sometimes the ordering is important, for instance, with our concat Robots. In these cases, you can add an index that starts at 1. You can also optionally filter by the multipart field name. Like in this example, where all files are coming from the same source (end-user uploads), but with different <input> names:
  
  Example:
```
"use": {
  "steps": [
    { "name": ":original", "fields": "myFirstVideo", "as": "video_1" },
    { "name": ":original", "fields": "mySecondVideo", "as": "video_2" },
    { "name": ":original", "fields": "myThirdVideo", "as": "video_3" }
  ]
}
```
  For times when it is not apparent where we should put the file, you can use Assembly Variables to be specific. For instance, you may want to pass a text file to 🤖/image/resize to burn the text in an image, but you are burning multiple texts, so where do we put the text file? We specify it via ${use.text_1}, to indicate the first text file that was passed.
  
  Example:
```
"watermarked": {
  "robot": "/image/resize",
  "use"  : {
    "steps": [
      { "name": "resized", "as": "base" },
      { "name": "transcribed", "as": "text" },
    ],
  },
  "text": [
    {
      "text"  : "Hi there",
      "valign": "top",
      "align" : "left",
    },
    {
      "text"    : "From the 'transcribed' Step: ${use.text_1}",
      "valign"  : "bottom",
      "align"   : "right",
      "x_offset": 16,
      "y_offset": -10,
    }
  ]
}
```
output_meta

Object / Boolean ⋅ default: {}

Allows you to specify a set of metadata that is more expensive on CPU power to calculate, and thus is disabled by default to keep your Assemblies processing fast.

For images, you can add "has_transparency": true in this object to extract if the image contains transparent parts and "dominant_colors": true to extract an array of hexadecimal color codes from the image.

For videos, you can add the "colorspace: true" parameter to extract the colorspace of the output video.

For audio, you can add "mean_volume": true to get a single value representing the mean average volume of the audio file.

You can also set this to false to skip metadata extraction and speed up transcoding.
format

String ⋅ default: "png"

The output format for the modified image.

The currently available formats are either "jpg" or "png".
direction

String ⋅ default: horizontal

Specifies the direction which the images are displayed. Valid directions include "vertical" and "horizontal".
border

Integer(1-10) ⋅ default: 0

An integer value which defines the gap between images on the spritesheet.

A value of "10" would cause the images to have the largest gap between them, while a value of "1" would place the images side-by-side.
background

String ⋅ default: "#FFFFFF"

Either the hexadecimal code or name of the color used to fill the background (only shown with a border > 1).

By default, the background of transparent images is changed to white.

For details about how to preserve transparency across all image types, see this demo.
adaptive_filtering

Boolean ⋅ default: false

Controls the image compression for PNG images. Setting to true results in smaller file size, while increasing processing time. It is encouraged to keep this option disabled.
quality

Integer(1-100) ⋅ default: 92

Controls the image compression for JPG and PNG images. Please also take a look at 🤖/image/optimize.
Before:

Quality 92 applied:

Quality 40 applied:

If this parameter is not specified, it will default to the quality of the input image. If we're unable to determine the quality, it will default to 92.

Merge several images into a single image

Parameters

`use`

`output_meta`

`format`

`direction`

`border`

`background`

`adaptive_filtering`

`quality`

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