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Reduction of image color is the process of decreasing the number of distinct colors used in an image. Instead of the potentially millions of colors available in a full-color image, a color-reduced image uses a smaller, limited set of colors. It can be a step in preparing a raster image to be used as a template for embroidery digitizing, where the number of thread colors is limited.
Studio provides a tool for reducing the color count in an image. It is accessible via the main menu > Image > Tools > Reduce Colors command.
A raster image placed in the background of the Work Area is typically used as a template to digitize an embroidery design from. Preprocessing the image can significantly speed up the digitizing process, especially for complex designs with many colors.
One possible approach is to convert the image from a full color scale to a limited palette of colors, thus getting a clear idea of the final thread count and their layout.
Original raster image - full color scale. We have to decide how many thread colors to use and how to place them.
Preprocessed raster image - reduced color scale. If we are happy with this layout, we can digitize it using 7 thread colors (the background is left empty).
The Color Reduction process uses a palette from which it takes the respective pixel colors.
A palette is a vertical column of color cells. The default palette has only two colors: 1. white and 2. black.
There are several ways to create a custom palette. The first step is to set the number of colors in the palette. Use the control with a tube icon to set the desired number of colors. This control can be used anytime to increase or decrease the color count in the palette.
When the number of colors is chosen, the colors themselves can be either automatically generated from the image (all at once), manually mixed, or picked one by one from the image. These methods can be combined.
Click the Automatic button to generate all palette colors at once automatically. The program chooses colors from the image and places them into the palette. This is a good starting point to create the palette, but often not the final step. Manual tweaking of individual colors is usually needed.
Each color can be manually defined or adjusted. Select a color cell and click the Mixer button or double-click the palette color cell to invoke the Color Mixer window. You can also use a long tap instead of the double-click.
Color Mixer window
To pick a palette color from the image, select a palette cell first. The cell will be highlighted. Then, click the image in the Work Area with the primary mouse button. The color from the clicked spot will be copied into the palette.
It is worth the time and effort to play with palette colors and tweak them to achieve a good color layout after reduction while keeping the color count low. Digitizing on top of such an image is much easier when doing a complex embroidery design.
Dithering is the replacement of a smooth color gradient with scattered pixels of palette colors. The amount of dithering can be set with the Dither control. When set to zero, no dithering is used. Dithering is useful when you want to digitize objects with color blending. In such cases, dithered zones serve as a guide to create the blending.
Dithering
Click the Preview button to check how the reduction with the current palette will look. The preview will appear on a secondary work area on the main control panel. The preview area allows you to zoom in and out and scroll or pan the preview.
The preview area displays a mask until the Preview button is clicked for the first time. A mask is a black-and-white picture generated from selected vector objects. Black means areas to be processed. White means excluded areas.
It is not necessary to convert the whole image at once. This may lead to unwanted interleaving of colors. Studio allows you to use common fill vector objects as a mask to mark areas of the image for color reduction. If you want to convert only part of the image to paletted colors, first draw fill or column objects on top of the image and select them. Then start the color reduction tool. The image will be converted only underneath the selected objects, which serve as a temporary mask and may be deleted after the image conversion.
For example, when preprocessing a photo of a tri-colored dog for embroidery digitizing, it is possible to mask each color range and repeat the color reduction to convert the photo to paletted colors in separate steps.
The advantage of such an approach is that you get a cleaner reduced image by using a different palette in each pass, for example: 1. black and dark gray palette, 2. brown palette, 3. white and cream palette, 4. pink palette (for tongue). These palettes are applied only to the respective masked areas and do not affect the rest of the image.
In this example a pink palette is used to reduce colors inside an area masked by a vector object. The rest of the image is untouched.
Note: you can use the Trace Tool to create complex mask objects easily.
Note: another way to simplify image colors is to use the Posterization tool.