Artwork Guidelines

Introduction
for all icons in the source tree, see Artwork.

A FreeCAD icon is composed of 6 elements which can be remembered by the acronym SALCHO: Stroke, Alignment, Lighting, Color, Highlighting, Outline.

Here's a concrete, yet arbitrary example:



The following sections explain these elements with more detail.

This icon is displayed as follows:

Colors
FreeCAD uses a palette adapted from the Tango palette. Each main color comes in 4 tones: Highlight, Base, Dark and Outline. Notice that the Outline is not completely black but a very dark variation of the Base.



See FreeCAD palette for the full range. A selection of some key colors.

Grid and stroke width
FreeCAD icons have a nominal size of 64 pixels both in width and height. When creating or editing an icon, make sure the document size is 64 x 64 with the units being pixels (px). Leaving an inner 2px margin of empty space all around the document area is useful as it prevents effects like anti-aliasing (blurring of edges). That is, the usable space for the icon should be considered 60 x 60, and the edges should be left empty.



It's also strongly recommended to use a visual grid that has a minor grid line every pixel, and a major grid line every 2 pixels. The strokes of the icon should be aligned along the minor grid intersections.

Strokes should be no thinner than 2px, with rounded caps and corners in most cases. Strokes can be thicker, but they should preferably be a multiple of 2px in order to minimize scaling fuzziness.



Outline
Basing yourself on the main color of the icon, ensure that there is a dark outline of 2px, as mentioned earlier. This works in unison with the highlight to ensure good form contrast on multiple background tones.



Highlight
Using the Highlight color, add an internal stroke of 2px to help make that outline pop. On dark backgrounds, it's this highlight what will be providing the form to the icon.



Lighting
As per Tango guidelines, if you're adding a gradient lighting effect, try to make it look like the light is coming from the top left. This is done by adding the highlight color up top left and the Base or Dark color bottom right. Notice that only palette colors are used.



Recommended recording format
All icons should be created in SVG format with a vector image application, such as Inkscape. This makes it easier to apply changes and derive additional icons in the same application space.

When committing icons to be used directly by FreeCAD (in a *.qrc file), save them as "Plain SVG". This will reduce the icon size and save the disk and memory space.

Closing remarks
Remember: SALCHO, Stroke, Alignment, Lighting, Color, Highlight, Outline

Here are some tips to check your work.

Checking size
Inkscape has a handy tool to check your icon at various sizes. Go to and it'll show you previews of your icon resized to 16, 24, 32 and 64 pixels.

Checking your outline

 * 1) Put your icon on a big rectangle that is the same color as the darkest color in your icon.
 * 2) Still looks OK? Great. Go to the next step. If not, adjust the highlight.
 * 3) Do the same but this time using the lightest color.
 * 4) Still looks OK? Great. Outlines and highlights have been used appropriately. Otherwise, adjust the outline.



Checking your contrast

 * 1) Export your icon from SVG to a bitmap format, like  or.
 * 2) Load your bitmap in an image program, and change it to grayscale. For example, in GIMP you would go to.
 * 3) Inkscape allows you to convert the SVG directly to grayscale using.
 * 4) Can you still clearly make out any internal details? Great. The contrast is good.

A grayscale image allows you to more easily identify problems in contrast, as only a mix of black and white is present. Testing grayscale images is also good for colorblind users. If they can see the details in a grayscale image, then the contrast of the fully colored image is probably good as well.