There’s a challenge making sure all images for a particular Image Set or App Icon are consistent. When the graphic designer wants to update an icon, they need to make sure they export each and every size. One vector graphic needs to be exported to as many as 30 image files.

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Part of the process of building an app for watchOS, iOS, or macOS is including all the image assets and app icons in your application. That could be done by exporting all the various sizes from your graphics application.

Speculid gives you the ability to run a script which builds those assets from a jpeg, png, or even vector graphics file like svg.


v2.0 ALPHA, BETA, OR DEVELOPMENT RELEASES you can download the latest version from the release page. Do not install using brew. ***

Speculid can be installed via Homebrew <>:

$ brew tap brightdigit/speculid
$ brew install speculid



v2.0 ALPHA, BETA, OR DEVELOPMENT RELEASES you will need to create a symbolic link manually or call the app using .../ Feel free to upvote issue #34. ***

$ speculid <file>
$ speculid --help
$ speculid --version

  -h --help     Show this screen.
  --version     Show version.

File Format

The .speculid file is a json file with the image set or app icon path, the graphic file source, and optionally the basic image geometry (width or height). Such as

  "set" : "Assets.xcassets/Raster Image.imageset",
  "source" : "layers.png",
  "geometry" : "128"


"set" : "Assets.xcassets/iOS AppIcon.appiconset",
"source" : "geometry.svg",
"background" : "#FFFFFFFF",
"remove-alpha" : true

Set set

Image Set Examples from Xcode

A set is an image set or app icon set used by Xcode. That path specified in the json could be relative to the .spcld file.

Source source

The image source file which could be a SVG or any bitmap image type compatible with imagemagick.

Geometry optional geometry

The destination geometry of image if needed (i.e. image set). It must be in the format of:

You can only specify the height or the width. The other dimension is automatically calculated based on the aspect ration of the image.

Background optional background

As a requirement, App Icons are required to exclude any alpha channels. In order to remove a transparency from a source png or svg file, you can specify to remove the alpha channel and add a background color. The background color can be set with a string in a standard rgb, rgba, or hex code format (#RRGGBB or #AARRGGBB). If no alpha is specified an alpha of 1.0 is assumed.

Remove Alpha optional remove-alpha

To specifically remove the alpha channel, a true boolean value must be specified. This will remove the alpha channel from the file. Make sure to specify an opaque background color when removing the alpha channel.

Application Configuration

If you install Speculid using the standard homebrew path, it should be able to find the nessacary applications needed. However if you need to set the path to the dependency applications, create a json file in your home directory /Users/username/ named speculid.json. Then specify the paths to the application dependencies:

  "paths" : {
    "inkscape" : "/usr/local/bin/inkscape",
    "convert": "/usr/local/bin/convert"

If you are uncertain the paths, in your terminal run which <command> and it will tell you the complete path to the application.

$ which inkscape

If you are interested in a more automated method, up vote the issue here.

Xcode Integration

With Speculid, the process of building image assets can be automated in Xcode.

  1. Add the speculid files to your source root as well as your source graphic files.

Xcode Target Membership

  1. Add the Run Script Build Phase to the top of your project with the following code:
  find "${SRCROOT}" -name "*.speculid" -print0 |
  while IFS= read -r -d $'\0' line; do
  speculid "$line" &

Xcode Build Phase Run Script

  1. Build the application. This will create the graphics which you will use in your asset image set or app icon.

Xcode Unorganized Assets

  1. Drag the images to the correct asset slot. Each rendered image file is suffixed denoting its slot.

(source file base name).(size)@(scale)~(idiom).(extension)


  1. Build and Run. Done.



Speculid © 2016, BrightDigit, LLC. Released under the MIT License.  ·  GitHub @brightdigit  ·  Twitter @brightdigit