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The Pixelate Filters
The Filter Pixelate submenu features a handful of commands that rearrange your image into clumps of color:Color Halftone: This highly practical filter allows you to suggest the effect of a halftone pattern. When applied to a CMYK image, Photoshop simulates a commercially reproduced color separation. Otherwise, the filter merely affects those channels that it can. For example, when working inside an RGB image, the Channel 4 value is ignored, because there is no fourth channel. When working on a grayscale image or mask, the Screen Angles value for Channel 1 is the only angle that matters.
Crystallize: This filter organizes an image into irregularly shaped nuggets. You specify the size of the nuggets by entering a value from 3 to 300 pixels in the Cell Size option.
Facet: Facet fuses areas of similarly colored pixels to create a sort of hand-painted effect.
Fragment: I already harped on this filter, so here's a quick summary. It jumbles, it bumbles, but more than anything, it dumbles.
Mezzotint: This filter renders an image as a pattern of dots, lines, or strokes. See the upcoming "Creating a mezzotint" section for more information.
Mosaic: The Mosaic filter blends pixels together into larger squares. You specify the height and width of the squares by entering a value in the Cell Size option box.
Pointillize: This filter is similar to Crystallize, except it separates an image into disconnected nuggets set against the background color. As usual, you specify the size of the nuggets by changing the Cell Size value.
The Crystal Halo effect
By applying one of the Pixelate filters to a feathered selection, you can create what I call a Crystal Halo effect, named for the Crystallize filter, which tends to deliver the most successful results. The following steps explain how to create a Crystal Halo, using the worlds in Figures 11-5 and 11-6 as examples.
STEPS: Creating a Crystal Halo Effect
Select the foreground element around which you want to create the halo. In my case, I select the world.
Choose Select Inverse. Or press Ctrl+Shift+I (z -Shift-I on the Mac). The halo appears outside the foreground element, so you have to deselect the foreground and select the background.
Press Q to switch to the quick mask mode. Now you can edit your selection and see the results of your changes.
Copy the mask. Press Ctrl+A and Ctrl+C to select the entire mask and copy it to the Clipboard. (That's z -A, z -C on the Mac.) We'll need this image later to complete the effect.
Choose Filter Other Minimum. As I explained in the preceding chapter, this filter enables you to increase the size of the deselected area. The size of the Radius value depends on the size of the halo you want to create. I entered 50 because I wanted a generous 50-pixel halo.
Choose Filter Blur Gaussian Blur. Then enter a Radius value equal to the amount you entered in the Minimize dialog box, in my case, 50 pixels. The result appears on the left side of Figure 11-5.
Figure 11-5: Create a heavily feathered selection outline (left) and then apply the Crystallize filter, invert the mask, and paste the original selection (right).
Choose Filter Pixelate Crystallize. Enter a moderate value in the Cell Size option box. I opted for the value 20 to convert the blurred edges to a series of chunky nuggets. The filter refracts the edges, almost as if you were viewing them through textured glass.
Invert the mask. Press Ctrl+I (z -I on the Mac) to swap the blacks and whites. This deselects the area outside the halo.
Paste the copied selection outline. Press Ctrl+V (z -V on the Mac) to paste the version of the mask you copied in Step 4.
Choose Edit Fade, and then Multiply. To blend the original mask with the crystallized version, press Ctrl+Shift+F (z -Shift-F on the Mac) and choose Multiply from the Mode pop-up menu. This burns one mask into the other, leaving only the halo selected, as in the right example in Figure 11-5.
Press Q to return to the marching ants mode. Then use the selection as desired. I merely pressed Ctrl+Backspace (z -Delete on the Mac) to fill the selection with white, as shown in the top-left image in Figure 11-6.
Figure 11-6: These images illustrate the effects of applying each of four filters to a heavily feathered selection in the quick mask mode, and then filling the resulting selection outlines with white.
Figure 11-6 shows several variations on the Crystal Halo effect. To create the upper-right image, I substituted Filter Pixelate Color Halftone for the Crystallize filter in Step 7. To create the lower-left image, I applied the Mosaic filter in place of Crystallize, using a Cell Size value of 14 pixels. Finally, to create the lower-right image, I applied Pointillize with a Cell Size of 5 pixels.
Creating a mezzotint
A mezzotint is a special halftone pattern that replaces dots with a random pattern of swirling lines and wormholes. Photoshop's Mezzotint filter is an attempt to emulate this effect. Although not entirely successful — true mezzotinting options can be properly implemented only as PostScript printing functions, not as filtering functions — they do lend themselves to some interesting interpretations.
The filter itself is straightforward. You choose Filter Pixelate Mezzotint, select an effect from the Type submenu, and press Enter or Return. A preview box enables you to see what each of the ten Type options looks like. Figure 11-7 shows off four of the effects at 300 ppi.
Figure 11-7: The results of applying the Mezzotint filter set to each of four representative effects. These line patterns are on par with the halftoning options offered when you select Mode Bitmap, as discussed back in Chapter 4.
When applied to grayscale artwork, the Mezzotint filter always results in a black-and-white image. When applied to a color image, the filter automatically applies the selected effect independently to each of the color channels. Although all pixels in each channel are changed to either black or white, you can see a total of eight colors — black, red, green, blue, yellow, cyan, magenta, and white — in the RGB composite view. The upper-left example of Color Plate 11-2 shows an image subject to the Mezzotint filter in the RGB mode.
If the Mezzotint filter affects each channel independently, it follows that the color mode in which you work dramatically affects the performance of the filter. For example, if you apply Mezzotint in the Lab mode, you again whittle the colors down to eight, but a very different eight — black, cyan, magenta, green, red, two muddy blues, and a muddy rose — as shown in the middle-left example of Color Plate 11-2. If you're looking for bright happy colors, don't apply Mezzotint in the Lab mode.In CMYK, the filter produces roughly the same eight colors that you get in RGB — white, cyan, magenta, yellow, violet-blue, red, deep green, and black. However, as shown in the bottom-left example of the color plate, the distribution of the colors is much different. The image appears lighter and more colorful than its RGB counterpart. This happens because the filter has a lot of black to work with in the RGB mode but very little — just that in the black channel — in the CMYK mode.
The right column of Color Plate 11-2 shows the effects of the Mezzotint filter after using the Fade command to mix it with the original image. I chose Overlay from the Mode pop-up menu and set the Opacity value to 40 percent. These three pairs of very different images were created using the same filter set to the same effect. The only difference is color mode.
