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Exploiting Filters part 1

Hacking Filters

There are literally thousands of Photoshop filters that you can purchase or download for free from the Internet. The filters are designed to cover a variety
of functions, ranging from filtering a file with preset settings, to adding ornamental edges, to analyzing a file scientifically.
Photoshop ships with no fewer than 105 filters, plus four panels that are also classed as filters. You can use the filters to create artistic effects or fake photographic
effects, or to optimize images for output. As far as usage goes, these filters can be split into four broad categories:
 – The standalone panels, such as Extract, Liquify, Pattern Maker, and Vanishing Point; used to extract, distort content, create custom patterns,
and clone in perspective, respectively
 – Those that can be applied through the Filter Gallery, such as Colored Pencil, Bas Relief, Grain, and so forth; used to create artistic effects
 – The filters that have their own dialog boxes and can accept custom settings, such as
Lens Correction, Smart Sharpen, and High Pass; used to optimize files for output
 – The filters that don’t have customizable settings, such as Despeckle, Sharpen Edges, Blur, and so forth; used to apply default settings for quick optimization

Some of the filters are very memory hungry and can take considerable time to calculate and to apply settings, especially when the allocated RAM has been consumed and efficiency is well
below 100% or you are working on large files in 16-Bits/Channel mode. In those circumstances, you can take some evasive measures before you apply a filter: purge clipboard, purge histories,
close Bridge (and other applications and utilities not being used currently, such as a browser or e-mail client), increase the amount of available RAM, or reduce number of fonts and plug-ins.
Decreasing or increasing the filter settings can also help. For instance, if you are using Palette Knife, decrease the Stroke Size or increase the Stroke Detail.

Applying RGB Filters to CMYK Files

A number of Photoshop filters work only on images in RGB color mode. So, what do you do, for example, if you want to apply the Stylize>Glowing Edges filter to an image in CMYK color
mode? Your first thought might be to change the color mode to RGB and then back again to CMYK. However, mode changes are usually not recommended while you’re editing an image
and should be preformed only as a last resort, or as a necessary step in a technique that will offset the damage that may be done by the mode change.
Here’s a little workaround that you can use that bypasses the need for a mode change.
1. In the Channels palette, select one of the channels.
2. Apply the filter, select another channel, and then use the keyboard shortcut Ctrl+F
(Windows),Ф+F to apply the filter again.
3. Apply the filter this way to all four channels.
Now when you click the composite channel, you will find that the filter has been applied to the
image as a whole and you have avoided a color mode change.

Reapplying Filter Settings

To reapply a filter using the previously used settings without first having to call the dialog box from the filter menu, press Ctrl+F (Windows),Ф+F (Mac OS). The shortcut works for only the
last used filter. If another filter has been used in the meantime, you have no choice other than to select the filter again from the filter menu. If you need access to the last used filter and its dialog
box, including the last-used setting, press Ctrl+Alt+F (Windows),Ф+Opt+F (Mac OS).

Filtering a Layer Nondestructively

When you apply a filter to a layer, the pixels change value and cannot be reverted without undoing all the edits that followed in its wake. The following workaround applies the filter to a layer
that can be positioned anywhere in the layer stack and acts as a poor man’s adjustment layer.
1. Create a new layer above the layer to which you want to apply a filter effect.
2. Fill it with 50% gray pixels (Edit>Fill>Contents Use: 50% Gray).
3. Set its blend mode to Overlay so that only the filter effect interacts with the layer
4. Apply the filter (Figure 18-1).

Graphic Pen filter

FIGURE 18-1: The Graphic Pen filter applied to a layer filled with 50% Gray, the layer’s blend
mode set to Overlay, duplicated and flipped horizontally and the opacity lowered to 50%.

This way of applying a filter makes it possible to modify the filter effect further by:
 – Using a layer blend mode other than Overlay
 – Duplicating the layer and then changing its blend mode
 – Reducing the layer’s opacity
 – Using the Blend If options found in the Layer Style dialog box
 – Turning the layer’s visibility off if the effect is no longer required

Unfortunately, not all filters listed under the Filter menu can be applied this way. However, applying textures via the Texturizer filter works extremely well. The results will also differ from
applying the filters directly to a layer, which is something to bear in mind. There is one other method you can use to apply a filter nondestructively, but it can be used only
in the current session. It involves the use of Smart Objects.
1. Select the layer to which you want to apply a filter effect.
2. Choose Group into New Smart Object from the Layers palette menu.
3. Double-click the layer thumbnail. Photoshop will open a temporary PSB document containing the layer content (you cannot apply a filter directly to a Smart Object, but
you can to the PSB document).
4. Apply the filter to the PSB document and save it.When you save the PSB document,Photoshop applies any changes you made to it to the parent file.

As long as you do not close the PSB document, you can revert it using its histories, apply another filter, and then save it again to apply the filter to the parent document. You can do this
as many times as you like without fear of damaging the original content.