Destructive Filters


Now that the constructive filters have displayed their image-correcting prowess, it s time for a little fun. The special effects in the Filter Distort, Pixelate, and Stylize submenus take your precious pixels and shove them about with wild impunity. With these filters, you can turn images inside out, explode and reassemble them, or boil the life out of them, leaving you with an indigestible goo. Used with care, they can be useful friends ; used unwisely, they ll turn on you viciously. These filters are undoubtedly the cool members of the gang; they look good and offer a fun night out, but ultimately they re not quite as responsible as the constructive filters. And some are just plain dumb.

Distort Filters

The common purpose of the filters in the Distort submenu is to transport pixels in your image across specifically defined patterns. For instance, Spherize gives the impression that your image has been wrapped around a ball. Twirl fixes the center point of your image and spirals the pixels around it, clockwise or counterclockwise. Shear provides an axis along which you can curve or lean your image.

The Distort filters are among the most memory- intensive of any of Photoshop s operations. To save yourself a lot of time watching the progress bar, do your experimenting with these filters on a lower-resolution version of your image. When you arrive at the effect you desire , make notes about the settings that produce the effect, and scale up those settings to apply the filter to your high-res version.

Note  

Filter values need to be greater for high-resolution images.

Diffuse Glow

Diffuse Glow seems to be misplaced in the Distort submenu, rather than among its kin, the Stylize filters. It gives the effect of viewing the image through a diffusion filter. You can set the level of Graininess, and define Glow and Clear parameters.

Glass

Glass, too, seems to belong elsewhere than with the Distort effects, perhaps among the Texture filters. Glass uses a hardwired variable displacement map effect similar to Distort Displace (see the Displace section later in this section). Its effect approximates viewing your image through a glass lens (defined in the Texture pop-up menu). You also have the option of applying a texture of your own, using the Load Texture dialog box. You ll find this option in some of the Effects filters as well. Look for it in Artistic Rough Pastels and Underpainting, Sketch Cont Crayon, and especially Texture Texturizer. These art effects offer a set of textures, but you can apply a pattern of your own making by saving it as a grayscale file in Photoshop format.

Ripple, Wave, and Zigzag Filters

Ocean Ripple, Ripple, Wave, and Zig Zag all offer methods of introducing degrees of wiggliness into your image. (Some might also include Glass in this group ; it applies a rippling effect with the added element of texture.) Of these, Wave is by far the most powerful and the most mysterious . Compare Zig Zag s user -friendly dialog with Wave s scientific control panel (see Figure 20.24).

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Figure 20.24: Compare the Zig Zag (left) and Wave (right) dialog boxes.

Wave

The Wave dialog is where some of Photoshop s mathematical underpinnings become most transparent. Too bad they couldn t provide a box with knobs you could twiddle like an old-fashioned synthesizer. You can input the number of wave Generators, define minimum and maximum Wavelength and Amplitude levels, Scale the wave effect horizontally and vertically, and choose between three Types of waves. And when in doubt, just click the Randomize button; Photoshop will make up its own wave parameters.

Figure 20.25 shows some of the effects that these filters can accomplish.

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Figure 20.25: Comparison of filter applications, left to right: Ripple, Ocean Ripple, Zig Zag, (Around Center), Wave

Pinch and Spherize

Pinch and Spherize are opposite sides of the same coin. If you apply a negative Amount in the Pinch dialog box, you get a Spherize-like effect; if you go negative in Spherize, the result is a lot like a Pinch (see Figure 20.26). The difference is that Pinch maps your pixels onto a rounded cone, whereas Spherize maps the image onto ”you guessed it ”a sphere. Spherize offers the added option of enabling you to constrain the effect to the horizontal or vertical axis, or both. These two filters don t cancel each other out, though. Compare the effects of each in Figure 20.27.

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Figure 20.26: The Spherize dialog box is similar to Pinch, except for the extra Mode (axis) option at the bottom.
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Figure 20.27: Pinched and Spherized images: (top left) Spherize, +100%; (top right) Spherize, “100%; (center) the original image; (bottom left) Pinch, +100%; and (bottom right) Pinch, “100%

Polar Coordinates

The Polar Coordinates filter takes the corners of your image and brings them together to form a circle (see Figure 20.28). Or the reverse: it takes the center and maps it out to the corners. Back in the old days, applying Polar Coordinates Rectangular to Polar was one of the few ways you could get type in a circle in Photoshop. Now that the Type tool offers that capability much more flexibly, Polar Coordinates can go back to what it does best: changing squares into circles.

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Figure 20.28: The Polar Coordinates filter applied to the prickly pear

Shear

Shear, as mentioned earlier, places your pixels along a curve. When you first open the Shear dialog box, you see a grid with a vertical line down the middle. You can take this vertical and angle it so it leans either way. This is akin to the Skew effect you get in the Transform functions. But if you click anywhere along the line, you can add points that turn the line to a curve. Now your image can distort along that curve in ways that Transform Skew and Distort can t achieve, as I ve done with the road in Figure 20.29. Radio buttons help you designate how the undefined areas will be treated: you can either wrap the image around or have the edge pixels repeat. If you don t like your curve, click the Defaults button and start over.

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Figure 20.29: The Shear dialog box

Twirl

The Twirl filter takes your image pixels and rotates them along a spiral. The center of the selection rotates while the edges remain in place. The Twirl dialog box (see Figure 20.30) offers two directions, expressed in minus and plus degrees, from 1 to 999. Because a circle is 360 , the full application of 999 gives you a spiral with almost three rotations . Applying a positive value maps the spiral in a clockwise direction, whereas applying a negative number twirls your image counterclockwise.

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Figure 20.30: You can Twirl from “999 to 999 .

Displace

The Displace filter is a bit different from others in the Distort submenu. It relies on the use of displacement maps to reconfigure your image pixels. Like Distort Wave, Displace retains quite a bit of its hard-science background, making it harder to predict without a lot of experimentation or mathematical know-how.

The Displace filter uses the brightness values in another image, called a displacement map, to relocate pixels. If the displacement map is a grayscale image with a single channel, pixels in the image that align with the black areas of the map are moved to the right and down, depending on your specifications in the dialog box. Pixels that align with the white areas of the map are moved to the left and up.

If the image has two or more channels, as in a grayscale image with an additional alpha channel or an RGB image, the first channel (Gray for grayscale and Red for RGB) determines horizontal movement and the second channel (an alpha channel for a grayscale image or the Green channel for an RGB image) determines vertical movement. The other channels in the image are not used. Areas of the image that align with the black pixels on the first channel are moved to the right, and areas that align with the white pixels are moved to the left. Areas of the image that align with the black pixels on the second channel are displaced down, and the areas that align with white pixels are moved up. Of course, the amount of displacement depends on the specifications you enter in the dialog box.

You can access Photoshop s displacement maps (find them in the Plug-Ins folder in the Photoshop application folder) or create your own. Displace lets you define horizontal and vertical scale, and you get to say how you want undefined areas to be handled. You can also tell Photoshop whether to tile the displacement map or scale it to fit your image.

Pixelate Filters

In general, the Pixelate filters break up and rearrange your image into variously shaped groups of pixels. As I mentioned previously, it would be impossible to fully describe every effect, let alone demonstrate them all visually. I ll just hit the high points here.

Facet, Fragment, and Color Halftone

Neither Facet nor Fragment offers a dialog box; they simply apply their effects without so much as a by-your-leave. Of the two, Facet has a more pleasing, irregular, sort of hand-colored effect. Color Halftone s controls include a Radius input, and four screen angles boxes. It takes an awfully long time to apply this clunky effect, which can be achieved with more finesse by choosing Filter Sketch Halftone Pattern.

Crystallize, Mosaic, and Pointillize

Crystallize, Mosaic, and Pointillize all offer a Cell Size slider in their dialog boxes, which enables you to designate how many pixels will be used to create a cell or clump of grouped color. Larger values result in great big groupings of pixels that rob your image of detail. Smaller values can create more interesting artistic effects, mainly by increasing color contrast from cell to cell .

Mezzotint

The Mezzotint filter offers several ways of adding largely uncontrollable noise to your image, in the form of dots, lines, or strokes. It s like the bullyish big brother of Add Noise without the slider. Mezzotint turns grayscale images black and white; RGB images are reduced to six colors (red, green, and blue, and their complements cyan, magenta , and yellow) plus black and white.

Figure C30a “e in this book s color section shows the effects of some of the Pixelate filters.

Stylize Filters

Some filters in the Stylize submenu deal with the edges of your image in one way or another; others map image pixels into geometric shapes .

Solarize

Solarize is unique in dealing solely with color shifts. Its effect is similar to combining a photographic negative with a positive. All blacks and white become black, grays remain gray, and other colors become their negative equivalent. You have no control over this filter.

Tiles and Extrude

Tiles and Extrude are the two Stylize filters that map to shape. Tiles breaks your image up into squares. You can define how many tiles fill a row across your image, how far the tiles can offset from each other, and how the areas between tiles will be filled. But the effect is rather flat; the Texture Mosaic Tiles filter creates a textured effect (with grouting options) that is much more realistic.

The Extrude filter is similar to Tiles, except that the mapping doesn t stay in two dimensions. The tiles or blocks extend into space. You can make your extruded elements block- or pyramid-shaped, and options are offered for the size and depth of the extruded shapes. In addition, you can decide whether you want incomplete blocks left out, and whether the fronts of square blocks should remain solid or contain image detail. Finally, you can arrange your extruded shapes randomly or arrange them by level. Figure 20.31 presents two sample Extrusions.

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Figure 20.31: The Extrude filter set with different options: (top) Blocks, Random, Solid Front Faces, and (bottom) Pyramids, Level-based

Find Edges, Glowing Edges, and Trace Contour

Find Edges, Glowing Edges, and Trace Contour all provide ways of seeing a color outline of your image. (Remember the technique of using High Pass and Threshold to create line art, and include that method in this repertoire of edge-building tricks.) Find Edges is a no-options effect that draws colored lines around the edges of your image. Glowing Edges does the same, except that you can determine the width, brightness, and smoothness of your edges. Look at the examples in Figure C31b in the color section, and notice that Glowing Edges, if left to its defaults, is nothing more than an inverted-color version of Find Edges. Or vice versa: if you want control over Find Edges, just use Glowing Edges instead and then invert the results.

Trace Contour creates colored contours but leaves all non-edge areas white (see Figure C31a in the color section). You can define a threshold above or below which Trace Contour will determine what constitutes an edge. This one seems to require a bit of fading and blending to make it interesting, whereas Find Edges and Glowing Edges produce a more visually appealing effect.

To practice using Stylize filters, you can use the file stylize.psd in the ch20 folder on the CD.

Diffuse

Diffuse works in a manner similar to the Dissolve brush or blending mode, in that it diffuses the edges of your selection. Because of this similarity, this filter s usefulness is rather limited; you can accomplish more by applying the brush or blending mode to an image. It does have a nice effect on type selections, though.

Wind

The Wind filter offers three strengths of wind effect: plain old Wind, a Blast of wind, or a Staggeringly strong wind, coming either from left or right. This filter is notoriously time-consuming , so try it on a grayscale or low-res image for a preview of the effect.

Emboss

And so we arrive at Emboss, perhaps Stylize s most interesting and entertaining offering. Figure 20.32 shows the Emboss dialog box with its Angle, Height, and Amount options. You can input your angle numerically , or slide the circle icon around to find the direction of light Emboss applies. Height is the distance of apparent bas relief you get, and Amount specifies the black-and-white value of edge pixels. Higher values create more contrast, and lower values give the image an overall gray cast.

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Figure 20.32: The Emboss filter dialog box

Emboss is one of those filters people really like to overuse on its own. Look at magazine ads and you ll recognize this frequently used effect. Its true power comes when applied to blended layers , or when applied individually to color channels. For an effect of color relief, use the Fade command and apply it by using the Hue or Luminosity mode. This enables you to retain the colors in your image, while enabling the Emboss effect to reveal itself.




Photoshop CS Savvy
Photoshop CS Savvy
ISBN: 078214280X
EAN: 2147483647
Year: 2004
Pages: 355

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