Maximizing and minimizing bright areas in an image You can increase or decrease light areas in an image with the Maxi- mum and Minimum filters. The Maximum filter adds light to shad- ows. The Minimum filter shrinks light areas. When you apply these filters, Canvas compares each pixel to its neighbors within the radius you specify, then replaces it with the lightest or darkest pixel in the group. Isolating images with the High Pass filter 1    With an image in edit mode, choose Image > Select > All. Then choose Edit > Copy. 2    Choose Image > Show Channels. 3    Create a new alpha channel by clicking the button in the lower-left corner of the Channels palette. 4    Select the new alpha chan- nel and choose Edit > Paste. 5    Choose Image > Filter > Other > High Pass and enter a radius value. Click OK. 6    Choose Image > Adjust > Threshold. Adjust the thresh- old until you outline the ar- eas you want. Click OK. 7    Paint areas white to include them in the selection. Fill the rest of the image with black. 8    Click the composite channel. Choose Image > Select > Load to load the alpha chan- nel and select an area. 9    In the example, the final im- age was finished by choos- ing Image > Select > Load with Inverse selected. 10 Then, choose Image > Filter > Blur > Gaussian Blur to apply a Gaussian blur of 3.0 pixels. Original Image High Pass filter Threshold filter Editing with Paint tools Finished alpha channel Isolated subject Tip To apply a choke or spread to an image manually, use the Maximum or Minimum filters in a color channel. Original Maximum 6 pixels Minimum 6 pixels
Canvas 8 Help: Image filters and effects (15 of 20)                                                 Page #721