Benefits
of the plugin

Trace edge lines and contours for graphics and design
Create a different kind of rasterization for Black& White prints & photocopies
Emulate traditional tone line lithfilm - with four different exposure directions
Change line width from 1 to 100 pixels for fluid lines etc.
Edge enhance photos in a snap

The Edge line filter plugin works with these image modes (Windows and Mac)...
8 & 16 bit / channel: RGB, Grayscale, Duotone, Multichannel.

Edge line
filter controls

This is the Edge line plug-ins control panel (Windows). Click on the image to enlarge. The controlpanel and preview area can be changed by dragging the sides.

The filter has these four sets of controls:

1. Method - choose between three unique ones
2. Clean-up - filter out noise or thin lines
3. Exposure - set the edge detection level
4. Output color - change the line or background color or use transparent background

Example -

The Edge line plugin is a handy tool for creating edge line or contour drawings.

It offers a few novel methods like tone line lith-film emulation with four exposure directions.

The plug-ins three methods

Soft multicolor

Tone line

Edge detection

The combo box lets you select one of three methods.

Soft Multicolor is a variation of the classic edge detection. algorithms with the improvement that it tends to draw the lines on the inside of edges instead of splashing out on both sides as Find Edges does.

Tone line Lithfilm emulates traditional tone line lithfilm prints with four different exposure directions.

Edge detection. is another variation of traditional edge detection methods.
Tone line and Edge detection produce two-colored outputs. The colors can be changed.
Soft multicolor has varicolored lines reflecting the originals color, but lets you change the background color. This method is best suited for edge enhancement and correction layers because it has softer lines which blend into the original more easily.

The plug-ins Exposure controls

Threshold



Line width



Exposure direction

Depending on the method, more or less of these control will be available.
Threshold, level is the minimum level of contrast required for the plugin filter to identify it as an edge. Soft Multicolor lets you control only this.
Width, pixels is the width of the drawn line (not the detected line) in pixels. Soft Multicolor does not allow you to change its line width, because it is not in the soft nature of the method to do so. The two other methods, however, do. Edgedetection performs best at line width 1, while Tone line can produce gorgeous results with large line widths.
Direction - this control is only available for the Tone line Lithfilm emulation method. The lines will appear somewhat as shadows cast in the exposure direction. Four directions are available.

Output color

Black on white



Color



Reset-button


Transparent background


Always edge trace before downscaling

These controls also vary with the selected method.

Black on white will draw in black lines against a white background. If using the method Soft Multicolor, then the lines will not be black, but the background will be set to white.
Color will let you select a color for the line and a color for the background. When used with the Soft Multicolor method, you will only be able to set the background color. The two colors will by default be set to the foreground and background colors in the host application. If you have changed the colors by clicking in the small colored rectangles, you can revert to the hosts foreground and background colors by clicking on the Reset button

Transparent background - this checkbox is only available if you work on a layer above the background. It is useful for all kinds of graphic design and when you want the output result to be saved as a gif image for web-design.

The portrait to the right has transparent background and is done with the Tone line method. If you have an image that's larger than the final result should be, then know it's always best to do edge lining before size reduction. This portrait was downscaled 400% after edge lining.

Soft Multicolor

Difference from Find Edges

This produces varicolored edge lines of varying thickness. Superficially it resembles traditional edge detectors like Find Edges, but where the traditional ones draw edge lines along both the outer and inner sides of an edge, we have changed it so that it tends to produce edge lines along the inside only. This produces no blur when the images are combined, in fact it sharpens images a lot (see below).

Also compared to other traditional methods like Find Edges, our method keeps lines thin which also gives sharper results. If you need thicker lines use Photoshop's Find Edges, but be warned it blurs or smears the result when overlayed.

The lines drawn will preserve some of the original color, which can be useful for correction layers since they blend in more naturally. Traditional Find Edges swaps colors from the inside of the edge to the outside and thus produces hazy results when doing edge enhancement layers.

Edge enhancement layers

Edge enhancement is a technique to trace edges with the intention of giving the photo a sharper and more defined appearance. It is good for web graphics and photos to be printed in catalogues etc. where the picture's impact depends on how articulate its objects are.

As you can see the original can be rather unsharp and the end result will still appear sharp and crisp. The end result has not been sharpened or modified beyond what is stated above. This means you can do considerable noise filtering on the original, yet still end up with a well articulated result.

Tone line (lithfilm emulation)

What is "Tone line"?

Tone line is a traditional darkroom technique involving two sheets of lithographic film, "lithfilm". Lithfilm has an extremely high level of contrast. The first sheet is a regular negative, the second is a negative of the first negative, hence a positive film. Since they are black/white and negatives of each other, if you place them on top of each other, no light would come through at a regular angle, but if viewed at an oblique angle a thin line of light would pass along edges.

Tone line is a printing technique that places the two lithfilm sheets together on top of a sheet of photographic paper. If you exposed directly from the top, no light would come through, but if you expose the paper from an oblique angle, light will pass through the thin celluloid film gap where edges meet.

The final tone line image depends on the direction of exposure. The exposure angle from the table will determine the width of the line and the direction determines which edges will be exposed.

The plug-ins tone line emulation

The "Exposure" frame of the control panel has a slider, "Direction, degrees" available when you use the lithfilm method. This slider lets you change the direction of exposure between 0, 45, 90 and 135 degrees and each produces very distinct results characteristic of the lithfilm tone line process. The slider "Width" is available for both methods.

Edge detection

This will simply trace all discernible edges with a line of definable width and color. It can roughly be understood as a tone line lithfilm exposed in all directions instead of just one.

It produces thicker lines than the Tone line method. These can be thinned with the Clean-Up options.

The plug-ins clean-up options

Clean up combo box

This combo box offers you the traditional clean-up methods thin, thin more and dilate.

They are best used with the strict two color methods, not Soft Multicolor.