Image filters

Image filters can be plugged in to enhance images during album generation, adding watermarking, logos etc. Image filters can be applied to closeup images, thumbnail images or both. Several filters can be chained to produce the desired effect. Imagine first applying red-eye reduction, then sharpening images and finally adding your logo to a corner. Well, all these filters are not written at the moment, but I expect them to show up: An open API and source code example are provided so developers easily can add new filters. Currently there is no graphical user interface for image filters, but with some fairly simple settings in the "User defined variables" section of the Advanced page, they can be controlled.

Quick example

Learning by example is powerful, so let's start by applying a grayscale filter to each thumbnail and add a copyright notice to the corner of each closeup image. (For a formal description of available filter features, see below.)

Start JAlbum and prepare a project for album creation. Now go to the Advanced page of JAlbum. There you will find a section called "User defined variables". We will use this section to set the properties of our filters. Enter exactly as this example shows. Pay attention to capitalization, ("GrayscaleFilter" is different to Grayscalefilter"). When done, remember to press ENTER to store the new settings.

Setting filter properties on the Advanced page

Thumbnail and closeup images processed through grayscale and text filters

The filters

Below is a list of the initially provided filters and their properties (features). New filters can be installed by putting their Java class files inside the plugins directory of JAlbum. All filters require the class property to be specified as filter identifier. All filters accept the thumbnails and closeups property that controls if the filter is to be applied to thumbnails only, closeups only or both. Default is both.

Grayscale filter

Converts images to grayscale.

Property	Values	Comment
class	GrayscaleFilter	Identifying filter name (required)
thumbnails	true|false	Apply to thumbnails?
closeups	true|false	Apply to closeups?

Logotype filter

Adds image/logotype on top of album images.

Property	Values	Comment
class	LogoFilter	Identifying filter name (required)
thumbnails	true|false	Apply to thumbnails?
closeups	true|false	Apply to closeups?
src	URL to jpeg or gif image	Any valid URL will do
align	left|center|right	Horizontal alignment of logotype (left)
valign	top|center|bottom	Vertical alignment of logotype. (top)
margin	Margin in pixels	Distance from edge of logotype to edge of image. (0)
offset	Horizontal offset in pixels	Fine tuning of placement. (0)
voffset	Vertical offset in pixels	Fine tuning of placement. (0)

Text filter

Adds texts to album images.

Property	Values	Comment
class	TextFilter	Identifying filter name (required)
thumbnails	true|false	Apply to thumbnails?
closeups	true|false	Apply to closeups?
text	Text to display	Allows JAlbum $variables like $originalDate and $comment to be embedded for dynamic content
color	HTML color definition	Understands common Netscape and Explorer color names like "pink", #rrggbb and r,g,b,a format
face	Name of font	Valid font names from your system like "Helvetica", "Verdana", "Courier New" etc
style	plain|bold|italic|bolditalic	Font style (bold)
size	Font size in pixels	(16)
antialias	true|false	Antialiasing gives smoother edges. (true)
align	left|center|right	Horizontal alignment of text (left)
valign	top|center|bottom	Vertical alignment of text. (top)
margin	Margin in pixels	Distance from edge of text to edge of image. (5)
offset	Horizontal offset in pixels	Fine tuning of placement. (0)
voffset	Vertical offset in pixels	Fine tuning of placement. (0)

Shadow text filter

Like text filter but also adds a drop shadow.

Extended properties (see TextFilter for the others):

Property	Values	Comment
class	ShadowTextFilter	Identifying filter name (required)
shadowColor	HTML color definition	Color of shadow. Understands common Netscape and Explorer color names like "pink", #rrggbb and r,g,b,a format
shadowDistance	Distance in pixels	(2)

Watermark filter

Like text filter but with a watermark effect.

Extended properties (see TextFilter for the others):

Property	Values	Comment
class	WatermarkFilter	Identifying filter name (required)
strengthPercent	Strength in percent	Controls watermark visibility. (20)

Adding filters to skins

Skins can be configured to automatically use certain filter settings. Simply save a project containing suitable filter settings in the "User defined variables" section, then rename the project file to hints.jap and put it in the skin folder. JAlbum will now load filter settings from this file when such a skin is selected. Remember to also strip the hints file from other settings that you don't want to be applied.

Developing filters

This section is for Java programmers who wish to extend JAlbum with new image filters. JAlbum image filters are java classes added to the plugins directory that implement the small se.datadosen.jalbum.JAFilter interface. A JAlbum filter should also adhere to the JavaBean specification, meaning:

• Provide a no-args constructor
• Getters and setter methods should follow the JavaBean naming convention.
• The filter should be serializable

The preferred way to pass parameters to a filter is to implement setter methods for them. By using a smart BeanShell script in the init.hsh file in the JAlbum program directory, JAlbum is capable of passing attributes from the user defined variables section of the Advanced tab page to the corresponding setter method of a filter.

The plugins JAlbum directory contains not only the filter classes but also the source code for the filters described on this page. Feel free to use them as base for your own filters. You will probably find the SimpleFilter below a good base for your own filters. The plugins folder also contains a compile.bat file that simplifies compilation for you. As you develop filters, please note that you do not need to restart JAlbum in order to refresh the filter classes as they are dynamically loaded every time an album is being processed. Finally, if you make a cool filter, please send it to me for inclusion.

Sample filter source code

The following simple filter adds a JAlbum logo to the corner of images:

import se.datadosen.jalbum.JAFilter;
import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;

/**
 * JAlbum simple image filter adding a JAlbum logo to the
 * corner of images
 * @author David Ekholm
 * @version 1.0
 */
public class SimpleFilter implements JAFilter {

    // Implements JAFilter
    public String getName() {
        return "Simple filter";
    }

    // Implements JAFilter
    public String getDescription() {
        return "Add a JAlbum logo to the corner of images";
    }

    // Implements JAFilter
    public BufferedImage filter(BufferedImage bi, java.util.Map vars) {
        Graphics2D g = bi.createGraphics();
        ImageIcon windowIcon =
         new ImageIcon(se.datadosen.jalbum.JAlbumFrame.class.getResource(
          "smallicon.gif"));
        g.drawImage(windowIcon.getImage(), 0, 0, null);
        return bi;
    }
}