Main Principle

Sfumato approximates graduation of brightness of image with density of stitches forming small curves and lines. On most dense areas, Sfumato uses fill stitches to avoid too short stitches. To achieve subtle graduation of brightness, Sfumato divides whole scale into 4 different shades: Darkest Thread Color (usually black), Dark Thread Shade, Light Thread Shade and Lightest Thread Color (usually white).

These colors may blend one into other. When creating multicolor design, Darkest and Lightest colors are common for all color scales. For example design in red and yellow scales would be sewn with following threads: black, white, dark red, light red, dark yellow, light yellow. Any of these colors can be omitted by proper adjustment of particular Threshold value.

The processing of image by Sfumato can be divided into following main steps:

1. Editing of image and elimination of backround in Painter.
2. Setting of design parameters.
3. Separation of image into color areas. These areas are displayed on Color Map.
4. Preview and calculation of design based on color layout of Color Map.

When separating image into color areas, Sfumato disregards brightness of image pixels and takes into account only the chromatic components of image, because brightness is later approximated by density and shades as described above. Therefore, chosen Palette Colors in More Controls window are devoid of brightness component. When Sfumato creates Color Map, it approximates all chromatic information of image with several Palette Colors from More Controls Window selected automatically or by user. 

Example of manual selection of Palette Colors. For below image (Eva), two color scales are sufficient. Two Palette colors (brown and teal) are placed into largest aggregations of image colors (red dots on Histogram). Green and black lines show how are the whole Histogram and Color Palette divided by colors reduction. Color Scales (upper picture) are created automatically from chosen Palette Colors.

Example of how Sfumato reduces the number of colors and how it separates chromatic and brightness components of an image.

• Picture on the left side is the original image.

• Picture in the middle is devoided of brightness information and number of color is reduced to chosen Palette Colors. There is Darkest Thread Color (black), Lightest Thread Color (white), brown Dark and Light Shades and teal Dark and Light Shades. Design has black outline.

• Picture on the right side is separated brightness map, which is used by Sfumato for calculation of stitch density. Brightness map is not visible for user.