Changing Color and Contrast

You can use the Invert, Desaturate, and Brightness/Contrast commands to create special effects and correct lightness levels in images. These commands apply changes equally to all color values.

If you select an area of an image, Canvas X Draw applies the command to that area only. Otherwise, Canvas X Draw applies the command to the entire image in a paint object.

Inverting Colors in Images

You can use the Invert command to reverse the colors in an image, as in a photographic negative. The command converts each pixel’s color to its opposite hue in the color spectrum. It does this by inverting the brightness value of each pixel in each color channel.

For example, if a pixel is pure red, its brightness levels are 255, 0, 0 in RGB mode. When inverted, this pixel’s brightness values become 0, 255, 255, changing it to pure blue-green, its opposite in hue.

Original RGB	Inverted RGB
Green channel selected	Inverted Green channel

The Invert command can be particularly useful in channel editing, as colored pixels can denote either masked or selected areas.

To Invert an Image:

1. Select one or more paint objects to invert all the images. You can select an area in one image in Edit mode to invert the selected area only. If you don’t make a selection, the entire image in Edit mode is affected.

You can’t use the Invert command on images in Indexed mode.

2. Choose Image | Adjust | Invert.

Desaturating Image Colors

You can use the Desaturate command to remove color from images completely, while retaining the relative brightness levels of shadows, midtones, and highlights. The command converts an entire image to shades of gray without changing the image mode.

To Desaturate an Image:

1. Select one or more paint objects to desaturate all the images. You can select an area in one image in Edit mode to desaturate the selected area only. If you don’t make a selection, the entire image in Edit mode is affected. This command works with paint objects in RGB Color mode, CMYK Color mode, and LAB Color mode.
2. Choose Image | Adjust | Desaturate, or select Desaturate from the Adjust menu in the Properties bar.

Adjusting Brightness and Contrast

You can adjust the brightness and contrast of an entire image or specific channels with the Brightness/Contrast command. Brightness refers to the lightness of an image. Contrast is the difference in brightness between two pixels.

Because the Brightness/Contrast command adjusts all pixels equally, you should avoid using it to lighten an image that appears too dark, because the image can lose shadow detail.

To Preserve Shadows or Highlights When Adjusting the Brightness of an Image:

Use the Levels or Curves commands. (See Levels and Adjusting Brightness Curves.)

To Use the Brightness/Contrast Command:

1. Select one or more paint objects to adjust all the images. You can select an area in one image in Edit mode to adjust the selected area only. If you don’t make a selection, the entire image in Edit mode is affected. This command doesn’t work with paint objects in Black & White mode or Indexed mode.
2. Choose Image | Adjust | Brightness/Contrast or select Brightness/Contrast from the Adjust menu in the Properties bar.
3. Enter a Brightness value from -100 to 100. Higher values can wash out midtones and shadows. Lower values can dull highlights.
4. Enter a Contrast value from -100 to 100. Increasing contrast moves the color values of pixels to the extremes of the brightness spectrum. Decreasing contrast moves color values toward medium gray.
5. After entering the settings you want, click OK.

See also:

• Levels
• Adjusting Brightness Curves
• Color Balance
• Color Equalization
• Hue/Saturation