Adobe 13101332 User Guide - Page 95

Adobe Photoshop Help Using Help | Contents | Index Working with Color Back 95 Making Grayscale and Bitmap mode conversions Refer to the following instructions for converting images between Grayscale and Bitmap mode. To convert an image to Bitmap mode: 1 Do one of the following: • If the image is in color, choose Image > Mode > Grayscale.Then choose Image > Mode > Bitmap. • If the image is grayscale, choose Image > Mode > Bitmap. 2 For Output, enter a value for the output resolution of the Bitmap-mode image, and choose a unit of measurement. By default, the current image resolution appears as both the input and the output resolutions. 3 Select one of the following bitmap conversion methods: • 50% Threshold, Pattern Dither, or Diffusion Dither to use a predefined conversion method. (See "Specifying predefined Bitmap conversion methods" on page 95.) • Halftone Screen to simulate the appearance of halftone dots in the converted image. (See "Specifying halftone screens for Bitmap-mode images" on page 96.) • Custom Pattern to simulate the appearance of a custom halftone screen in the converted image. (See "Specifying custom halftone screens for Bitmap-mode images" on page 97.) To convert a Bitmap-mode image to grayscale: 1 Choose Image > Mode > Grayscale. 2 Enter a value between 1 and 16 for the size ratio. The size ratio is the factor for scaling down the image. For example, to reduce a grayscale image by 50%, enter 2 for the size ratio. If you enter a number greater than 1, the program averages multiple pixels in the Bitmap-mode image to produce a single pixel in the grayscale image. This process lets you generate multiple shades of gray from an image scanned on a 1-bit scanner. Specifying predefined Bitmap conversion methods The predefined conversion options in the Bitmap dialog box determine the quality of the converted image. 50% Threshold Converts pixels with gray values above the middle gray level (128) to white and below to black. The result is a very high-contrast, black-and-white representation of the image. Pattern Dither Converts an image by organizing the gray levels into geometric configurations of black and white dots. Using Help | Contents | Index Back 95