SDF-Generator

SDF-Generator

Command line tool to bulk generate signed distance fields from images.

The tool produces images with 1 channel of 16 bit (Gray16 in Golang).

References

• The SDF generation is based on DistanceFieldGenerator.java from LibGDX (Apache 2.0).
• The example icons are part of Material Design Icons (Apache 2.0) from Google.

Command line parameters

=== SDF Generator (github.com/maxfish/sdf-generator) ===
Usage of ./sdf-generate:
  -channels string
    	Specify which channels of the input image can contribute to defining the "inner" area of the shape.
    	Accepted values are R,G,B,A and they can be specified separated with a comma.
        E.g. 'R,A' means that the algorithm will consider a pixel "inside" the shape if the Red channel,
        or the Alpha channel, are above the threshold.  (default "A")

  -crop
    	Specify if the resulting image should be cropped.

  -downscale int
    	Sets the factor by which to downscale the image during processing. The output image will be smaller
        than the input image by this factor, rounded downwards. Note: For greater accuracy, images to be used
        as input for a distance field are often generated at higher resolution. (default 1)

  -input string
    	Specify an input filename or a folder path.

  -output string
    	Specify an output filename or a folder path. If input is a path then output must be a path.

  -overwrite
    	Specify if the output file, when it already exists, can be overwritten.
    	WARNING: this flag is applied to the whole operation and it can delete many pre-existing images.

  -spread float
    	Specify the spread of the distance field. The spread is the maximum distance in pixels that will be
        scanned looking for a nearby edge. (default 4)

  -threshold float
    	Specify the threshold applied to the channels for one pixel to be considered "inside" the source shape.
    	The accepted values go from 0.0 to 1.0. (default 0.5)

  -alpha bool
    	Output the signed distance field to the alpha channel instead of using gray color values. (default false)

Example

Process a whole folder:
./sdf-generate -input example/input -output example/output

Process a single image:
./sdf-generate -input example/input/ic_backup_black_48dp\ 2.png -output example/output/test.png

Results

Input image	Output image

• The image is correctly centered in the resulting file
• Images with content touching the edges (the case above) are correctly handled
• The resulting image is bigger than the original one (with downscale=1) because space is made available for the spread
• Currently, only 1-channel images are produced (Gray16)

A couple of common wrong results generated by similar tools:

Image	Problem
	Spread outside of the boundaries. It is cut on both the left and the right sides.
	Image not centered