Adobe 65089063 User Guide - Page 214

206 CHAPTER 9 Applying Filters and Effects Other filters Filters in the Other submenu let you create your own filter effects, use filters to modify masks, offset a selection within an image, and make quick color adjustments. Custom Lets you design your own filter effect. With the Custom filter, you can change the brightness values of each pixel in the image according to a predefined mathematical operation known as convolution. Each pixel is reassigned a value based on the values of surrounding pixels. You can save the custom filters you create and use them with other Photoshop images. To apply a Custom filter effect: 1 Choose Filter > Other > Custom, or use the Filters palette to apply the Custom filter. 2 Select the center text box, which represents the pixel being evaluated. Enter the value by which you want to multiply that pixel's brightness value, from -999 to +999. 3 Select a text box representing an adjacent pixel. Enter the value by which you want the pixel in this position multiplied. For example, to multiply the brightness value of the pixel to the immediate right of the current pixel by 2, enter 2 in the text box to the immediate right of the center text box. Note: To avoid turning the image completely white or black, the sum of the values in the matrix should equal 1. 4 Repeat steps 2 and 3 for all pixels to include in the operation. You don't have to enter values in all the text boxes. 5 For Scale, enter the value by which to divide the sum of the brightness values of the pixels included in the calculation. 6 For Offset, enter the value to be added to the result of the scale calculation. 7 Click OK. The custom filter is applied to each pixel in the image, one at a time. Use the Save and Load buttons to save and reuse custom filters. DitherBox™ Creates a custom dither pattern for a selected RGB color. (See "Creating and applying custom dither patterns" on page 237.) High Pass Retains edge details in the specified radius where sharp color transitions occur and suppresses the rest of the image. (A radius of 0.1 pixel keeps only edge pixels.) The filter removes low-frequency detail in an image and has an effect opposite to that of the Gaussian Blur filter. It is helpful to apply the High Pass filter to a continuous-tone image before using Image > Adjustment > Threshold or converting the image to Bitmap mode. The filter is useful for extracting line art and large black-and-white areas from scanned images. Minimum and Maximum Are useful for modifying masks. The Minimum filter has the effect of applying a spread-spreading out black areas and shrinking white areas. The Maximum filter has the effect of applying a choke-spreading out white areas and choking in black areas. Like the Median filter, the Maximum and Minimum filters look at