Extended Image Properties

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Contents

Overview

Adobe Photoshop is one of the world's best known software applications and widely used in professional graphics both in print and for web work. One of the sources of its power is the native PSD file format. A PSD file can not only hold image data, but is more of a large container which can include metadata, camera info, text, vector artwork and more. Most other programs only handle a small subset of its capabilities.

Scribus has native capabilities to import PSD files from version 6 and earlier, the latest version of the PSD format for which the specifications have been published. Beyond importation, the support is quite extensive, including the ability to manipulate and adjust layer settings, and optionally enable and use masking along with the paths embedded in the file. In almost all cases, any embedded ICC color profiles which are not defective are detected and used when color management is enabled. Files saved from newer versions should work without major issues, but they may have file format features which are not publicly documented.

Layers

Like many other image editing programs, Photoshop can handle layers, and the PSD format stores them. The context menu for image frames containing a PSD file will show an entry which is not available for other image formats: "Extended Image Properties". The related dialog contains two tabs, "Layers" and "Paths". Let's have a look at the "Layers" tab first.

Similar to layers in Scribus, you can switch layers in PSD files on or off. This will not change the original file, but only affect its use in Scribus. In our example we have loaded a PSD file with three layers, as can be seen on the screenshot below. Scribus shows the name and a small preview of each layer:

Image:Psd-layers1.png

"Layer 1" is the background of the whole image, and we switch it off by unchecking it in the row with the eye symbol:

Image:Psd-layers2.png

The utility of PSD files begins to show itself when you consider, for instance, that an image can contain layers for different slogans for the same image or different language or color versions. Many PSD files created by professionals contain dozens of layers, and you can easily switch them on or off in Scribus. Beware, though, that files with many layers may slow down the process of checking and unchecking single layers.

Blend Modes and Opacity

Blend Modes and Layers

Layers can interact with each other in different ways. These different ways are determined by so-called blend modes. A blend mode tells a program such as Photoshop or Scribus how a pixel on an upper layer will influence the matching pixel on the layer below. Blend modes can be used to improve existing images, but also allow for some fascinating effects. If you have a layered PSD file, you will have the same blend modes available as in Photoshop, GIMP or other image editors. If you wish to become proficient in using blend modes, experience and experimentation are going to be your best teachers, since a manual, no matter how detailed, cannot beat experience in this area of image editing. Note that the use of blend modes requires a fast processor. If your computer has a slow CPU, you should expect some delay when you're applying them.

Normal

"Normal", while the default setting, is not exactly a blend mode. It treats both layers as if they were separate images. To let them "interact", you have to change the opacity of the upper layer, thus acting like you would with two overlapping image frames.

Darken

"Darken" does a pixel-for-pixel comparison between two layers and selects the darker pixel for display.

Image:Blend-darken.png

Lighten

"Lighten" does a pixel-for-pixel comparison between two layers and selects the lighter pixel for display.

Image:Blend-lighten.png

Hue

This uses the hue (color) of the upper layer for the lower layer. Saturation and luminance remain unchanged.

Image:Blend-hue.png

Saturation

"Saturation" uses the saturation of the upper layer for the lower layer. Hue and luminance remain unchanged.

Image:Blend-sat.png

Color

"Color" uses the hue and the saturation of the upper layer for the lower layer. Luminance remains unchanged.

Image:Blend-colour.png

Luminosity

"Luminosity" uses the luminance of the upper layer for the lower layer. Hue and saturation remain unchanged.

Image:Blend-lum.png

Multiply

This mode multiplies the value of the pixel on the lower level with that of the upper level, resulting in a darker image.

Image:Blend-multiply.png

Screen

"Screen" multiplies the inverse value of the pixel on the lower level with that of the upper level, brightening the image.

Image:Blend-screen.png

Dissolve

"Dissolve" colorizes the lower layer with the colors of the upper layer. The degree depends on the level of transparency, as it only works for at least partially transparent pixels.

Image:Blend-dissolve.png

Overlay

"Overlay" combines features of the "Screen" and "Multiply" modes. It shows patterns or colors of the selected layer while preserving shadows and highlights of the underlying layer.

Image:Blend-overlay.png

Hard Light

"Hard Light" also combines features of the "Screen" and "Multiply" modes. It's used to show highlights and shadows.

Image:Blend-hardlight.png

Soft Light

"Soft Light" combines features of the "Color Dodge" and "Color Burn" modes. It produces soft shadows and highlights.

Image:Blend-softlight.png

Difference

"Difference" subtracts the selected layer color from the underlying layer, depending on which is lighter.

Image:Blend-difference.png

Exclusion

"Exclusion" is similar to "Difference", but softer.

Image:Blend-exclusion.png

Color Dodge

The lightness values of the colors in the selected layer modify the underlying colors, by making them lighter. Black produces no effect.

Image:Blend-cdodge.png

Color Burn

The lightness values of the colors in the selected layer modify the underlying layers, by making them darker.

Image:Blend-cburn.png

Clipping Paths

Clipping paths are vector shapes which are stored in PSD files. They are mostly used to indicate the real shape (other than the rectangle of the image itself) of content. Scribus can read those clipping paths and use them. On the screenshot below you see a PSD file with a white background:

Image:Clip-path1.png

Opening the "Editing Extended Image Properties" dialog from the context menu reveals that the image file contains a clipping path called "Pfad 1", and it also shows a preview of its shape. If you click on it, the path will be activated and the background is "clipped". Note that you can use only one clipping path per image.

To revert the clipping, click "Don't use any Path".

If you want to use clipping paths in PSD files by default, you can use the "Tools" tab for images in the Document Setup/the Preferences and check "Use embedded Clipping Path".

Image:Clip-path2.png

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