The /image/facedetect Robot

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The /image/facedetect Robot detects faces in images and returns their coordinates, or cuts them from the original images and returns those as new images.

Parameters

Name Type Default Description
use (required) String / Array of Strings / Object

General

Specifies which Step(s) to use as our input.

Special Step names

A special Step name is ":original", which provides user uploads handled by Transloadit. Outside of this restriction you can pick your own names.

Providing several Steps as input

You can add arrays to use several Steps:
"use": [
  ":original",
  "encoded",
  "resized"
]
:bulb: 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, the /file/compress Robot 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 the /video/adaptive Robot, 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 the /file/compress Robot 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 the /media/playlist Robot 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, the /video/merge Robot 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 the /image/resize Robot to burn the text in an image, but you are burning multiple texts, so where do we put the text file? We use 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,
    }
  ]
}
crop Boolean false Determine if the detected faces should be extracted. If this option is set to false, then the Robot returns the input image again, but with the coordinates of all detected faces attached to file.meta.faces in the result JSON. If this parameter is set to true, the Robot will output all detected faces as images.
crop_padding String "5px" Specifies how much padding is added to the extracted face images if crop is set to true. Values can be in px (pixels) or % (percentage of the width and height of the particular face image).
format String "preserve" Determines the output format of the extracted face images if crop is set to true. The default value "preserve" means that the input image format is re-used. Valid values are "jpg", "png", "tiff" and "preserve".
min_confidence Integer(0-100) 70 Specifies the miminum confidence that a detected face must have. Only faces which have a higher confidence value than this threshold will be included in the result.
faces String / Integer "each" Determines which of the detected faces should be returned. Valid values are:
- "each": Each face is returned individually.
- "max-confidence": Only the face with the highest confidence value is returned.
- "max-size": Only the face with the largest area is returned.
- "group": All detected faces are grouped together into one rectangle that contains all faces.
- any integer: The faces are sorted by their top-left corner and the integer determines the index of the returned face. Be aware the values are zero-indexed, meaning that faces: 0 will return the first face. If no face for a given index exists, no output is produced.

For the following examples, the input image is:

faces: "each" applied:


faces: "max-confidence" applied:


faces: "max-size" applied:


faces: "group" applied:


faces: 0 applied:

Demos

Our /image/facedetect Robot can be used in combination with other Robots, to create powerful workflows unique to your use case. Here are a few example scenarios that you can try live on our website:

Pricing

Transloadit is a SaaS with a subscription model.

Our /image/facedetect Robot counts towards your plan's data at a normal rate. It charges at minimum 1MB whenever it is used. Assuming the Startup Plan and an average image size of 0.8MB, you could detect 8192 images for $49/month.

Just like with your mobile plan, pricing goes down considerably when you commit to larger monthly volumes. You can adjust this every month. More info and available plans on our Pricing page.

Blog posts about the /image/facedetect Robot

We wrote the following posts about the /image/facedetect Robot on our blog: