Changing Color Modes
Before converting your file to a different color mode, it's a good idea to save a "master" version of your photo first. That way, no matter what changes you make to your image, you always have an untouched backup version, just in case.
To convert an image to grayscale:
- From the Image menu, select Mode > Grayscale (
Figure 3.5 Choose Image > Mode > Grayscale to convert an RGB image to grayscale. A grayscale image is only about 1/3 the size of an RGB image.
- Click OK (
Figure 3.6 In order to convert from RGB to grayscale, you will discard the color information. Before you convert an image to grayscale, you may want to save a separate version to preserve the colors in the original image file.
To convert an image to bitmap:
- From the Image menu, select Mode > Bitmap (
Figure 3.7 Choose Image > Mode > Bitmap to convert an image to bitmap (black and white) mode.
- Click OK to convert the image to grayscale (
Figure 3.8 Before converting to bitmap mode, your image is converted to grayscale.
Figure 3.9 The Bitmap dialog box.
- If desired, enter a value for the output resolution. The default value is the current resolution of the image, which is usually fine for most purposes, and need not be changed during this conversion.
- From the Use pop-up menu, choose from one of the following three conversion methods to complete the bitmap conversion:
- 50% Threshold converts pixels above medium gray to white, and below medium gray to black, resulting in a high-contrast image (
Figure 3.10 50% Threshold results in a high-contrast image.
- Pattern Dither converts areas of gray into geometric patterns (
Figure 3.11 Pattern Dither creates geometric patterns based on areas of gray.
- Diffusion Dither results in a grainy, graphic look (
Figure 3.12 Diffusion Dither results in a grainy, posterized look.
- 50% Threshold converts pixels above medium gray to white, and below medium gray to black, resulting in a high-contrast image ( Figure 3.10 ).
- Click OK to convert the image to bitmap mode.
To convert an image to indexed color:
- From the Image menu, select Mode > Indexed Color (
Figure 3.13 Choose Image > Mode > Indexed Color to convert an RGB image to indexed color.
- Choose Palette, Dither, and other options displayed in the dialog box (
Figure 3.14 The Indexed Color dialog box includes options for choosing colors, palettes, and dithering. This figure shows the dialog box on a Macintosh.
- Click OK to confirm your choices.