June 2009 Archives

The median filter tends to preserve edges, which is good but it also tends to round corners, which is sometimes not so good. Unless you want that effect. Then it's actually pretty interesting.

As an experiment I tried it at various settings on a stochastic FM screened halftone. I like some of the results.

Median Filter radius = 3

This one is pretty crazy. Like a circuit board. It would be time consuming to make any other way.

Median Filter radius = 2

Median Filter radius = 1

UPDATE 7/14/2009

The median filter's behavior in the first image is so transformative, and so neighbor-dependent, that it reminds me of John Conway's Game of Life algorithm. It makes me want to implement the Game of Life in Photoshop.

...and as I look, not only do I find it's been done, but quite recently.

Even has a closeup of an eye represented by a stochastic halftone. That's kind of eerie.

We have the same eyeglasses. lol

If random points on a plane are post offices, then Voronoi Diagrams divide the plane into the most efficient zip codes.

I found a Voronoi diagram on the internet. I duplicate its calculation here using Photoshop's 'Lighten' blend mode and some radial grads.

Voronoi Diagram by Paul Herron

UPDATE 9/16/2009

How to: Draw the Voronoi Diagram

UPDATE 9/27/2009

Visualizing the Distance to the Nearest McDonalds Restaurants

Weather Sealed: Where the Buffalo Roam

UPDATE 10/6/2009

This Voronoi Diagram traveling matte effect is pretty cool.

The Dissolve blend mode turns blurry edges speckly. The median filters turns speckly edges rough.

Good for torn paper, grungy type, rough edges.

I make a hexagonal grid in Photoshop from regular equilateral triangles.

I then extend the technique to demonstrate how to make a hexagonal (triangular) mosaic without the use of special plugins or anything more than the standard Photoshop square mosaic tile filter.

I plan to use these techniques in conjunction with the 17 Wallpaper Group Plane Symmetries of programs like Artlandia Symmetryworks, TileBuilder, or Xaos Terrazzo to make even more elaborate pieces.

More on the topic of Distorting Photoshop Filters Without Distorting the Underlying Image

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Shawn Hargreaves has an interesting approach to hexagonal mosaics: he makes a Photoshop displacement map that fools every pixel in a hexagonal region from getting its color from the same pixel. I prefer an area average to a single pixel sample - that way a fleck of noise can't influence a whole hexagon - but the results look pretty good, and I like the ingenuity of the idea.

I was intrigued by the Photoshop dual brushes, but I was unable to find too much information about them.

I notice they combine two simple brushes through the use of a blend mode.

I can combine two brushes through a blend mode myself directly in Photoshop without using dual brushes if I want some kind of static new brush footprint. What I want to see is a brush behavior that is unique to dual brushes, and that cannot be duplicated through the use of a specially prepared combination brush sample.

The hard mix blend mode has a threshold behavior. It forces grays to either black or white. I wanted to see if I could use the hard mix blend mode and a Photoshop dual brush to create a brush that has mode bristles when I apply more pressure.

Not darker bristles. Not a bigger bristle footprint. More bristles in contact with the canvas.

The Photoshop 'Dissolve' blend mode reduces a layer to random dots in a density based on that layer's opacity. If the layer opacity is controlled by a grayscale image layer mask, then a simple stochastic halftone can be produced.

More on halftones in Photoshop (using the 'Hard Mix' blend mode)

More on using the 'Dissolve' blend mode (for additive color mixing)

UPDATE 6/29/2009

For comparison here is a real stochastic error diffusion FM frequency modulated halftone screen made by putting together three Photoshop bitmaps.

Click to see pixels at 100% - they are brighter - downsampling to fit the blog layout artificially darkened the image.

A simulation of additive RGB color mixing using the Photoshop dissolve blend mode.

Photoshop uses the same pixel patterns for a given opacity for each layer, so you have to build from the bottom up...

Set the base layer to 100% opacity.

Set the middle layer to 67% opacity. That will reveal 1/3 of the base.

Set the highest level to 33% opacity. That will reveal 2/3 of the mix of the first two.

Now you have each of the 3 layers revealed at 33% coverage.

I was unable to simulate subtractive CMY color mixing using the Photoshop dissolve blend mode.

UPDATE

It occurs to me that a highly magnified (nearest neighbor algorithm) blow-up of 16x16 pixel images of dissolve pixels in the right opacity proportions would be a great way to make the masks that randomly 'texture bomb' (shuffle) the 'Truchet tile'-style maze described here.

UPDATE

I see the same pixel patterns for a given opacity on multiple images (or the same resolution) - it doesn't randomize for each new file. So if you want to images of random pixels it may be best to (for example) cut them from different places in a larger image.

click image for a closer view

An experiment in combining CMY subtractive color channels into a full color image using Photoshop's Normal blend mode.

The bottom layer must be set to 100% (one over one)

The middle layer must be set to 50% (one over two)

The top layer must be set to 33% (one over three)

This effectively averages the images into a 1/3 intensity composite. A final 300% dimming curve (pinned at white and deepening the blacks) compensates.

The subtractive primaries do not really want to mix in this way. The fact that I was able to do so relies on the final compensating curve that pins white at white and drops black severely. I'm not sure that effect could be reproduced in the real world.

click image for a closer view

An experiment in combining RGB additive color channels into a full color image using Photoshop's Normal blend mode.

The bottom layer must be set to 100% (one over one)

The middle layer must be set to 50% (one over two)

The top layer must be set to 33% (one over three)

This effectively averages the images into a 1/3 intensity composite. A final 300% brightening curve compensates.

I expected the multiply blend mode to properly combine CMY separations into full color images.

It does.

I was surprised to see how well the difference and exclusion blend modes accomplished the same task. You may assume it's because they are subtractive in nature, and so should be expected to perform subtractive color mixing, but in fact they mix pairs of colors in surprising and unnatural ways.

More on blend modes.

A brief 2D simulation of metaballs, a/k/a 'blobbies,' using Photoshop, a gradient map, and various blend modes including the linear dodge (add), lighten, screen and difference blend modes.

digg.com ran a feature tonight called If David Lynch directed Dirty Dancing... which (I was surprised to see) began with a :05 animation of a logo for Vestron Pictures that I worked on back in the 80's.

I thought I had a clipping from a trade magazine called Computer Pictures, so for fun I dug it up.

We ran that thing on a Cray supercomputer - and, yes, that's the originator of the Perlin Noise Function as one of the TD's.

UPDATE 7/27/2009

...and interestingly, given the recent resurgence in interest in TRON, Jan Carlee, Christine Chang, Ken Perlin and Josh Pines (not mentioned above, but should have been) were all on the original TRON cg animation crew at MAGI

I refuse to accept the explanation that the Exclusion Photoshop blend mode is simply a watered down, low contrast version of the Difference blend mode, suitable for nothing more than image alignment. There has to be a 'killer app' for this blend mode.

One such 'killer app' is its ability to capture midtones in images, and its ability to isolate the edge regions of soft masks.

(another way to create an outline)

Midtones and edge outlines are both useful as masks for color correction.

Photoshop's Hard Mix blend mode seems nearly useless. It does have one 'killer application,' however.

The killer app for Photoshop's Hard Mix blend mode is creating halftones.

Here is a brief tutorial in how to create custom halftone effects in Photoshop using a gray scale photo, a grayscale pattern, and the hard mix blend mode.

I'm compiling a list of all Photoshop blend mode killer apps here

Blend Mode Killer Apps

I'm compiling a list of blend mode tutorials. It is incomplete for now. I'll add to it over time.

I'm particularly interested in the 'killer app' for each blend mode, and the best way to demonstrate it. I think that any collection of tutorials that uses the same pair of images and only varies the blend mode combining them is not demonstrating each mode in the best possible way.
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The Normal Blend Modes

• Normal

Additive RGB Color Mixing using Photoshop Normal Blend Mode

Subtractive CMY Color Mixing using Photoshop Normal Blend Mode

• Dissolve

I used dissolve to create the chalky white line in this illustration

A Simulation of Additive RGB Color Mixing using the Dissolve Blend Mode

The Darken Blend Modes

• Darken
• Multiply

Multiply Blend Mode | What it is and why you need itSome Thoughts on Photoshop Multiply,

Soft Light, Overlay Blend Modes

Photoshop Screen and Multiply Blend Modes as Logic Gates

Additive Color vs Subtractive Color

Color Transparency in Computer Graphics

Colorize Black & White Art by Keymixing

Creating an Outline

Subtractive Color Mixing using Multiply, Difference and Exclusion

• Color Burn
• Darker Color

The Lighten Blend Modes

• Lighten

• Screen

Screen Blend Mode | What it is and why you need it

Photoshop Screen and Multiply Blend Modes as Logic Gates

Additive Color vs Subtractive Color

• Color Dodge
• Linear Dodge (Add)

Additive Color vs Subtractive Color

Simulating 2D Metaball Blobbies with Photoshop

Compositing Premultiplied 3D CG in Photoshop

Colorize Black & White Art by Keymixing

• Lighter Color

The Contrast Blend Modes

• Overlay

Some Thoughts on Photoshop Multiply, Soft Light, Overlay Blend Modes

Overlay and Softlight are good for non-destructive dodging and burning. Float a gray layer above your image and 'carve' it with lighter and darker grays

• Soft Light

Overlay and Softlight are good for non-destructive dodging and burning. Float a gray layer above your image and 'carve' it with lighter and darker grays

Some Thoughts on Photoshop Multiply, Soft Light, Overlay Blend Modes

• Hard Light
• Vivid Light
• Linear Light
• Pin Light
• Hard Mix

Custom Halftone Pattern in Photoshop

Hard Mix Photoshop Blend Mode Killer App

Photoshop 'hard Mix' Dual Brush

The Inversion Blend Modes

• Difference

Difference vs Exclusion Photoshop Blend Mode Killer App

Subtractive Color Mixing using Multiply, Difference and Exclusion

• Exclusion

Difference vs Exclusion Photoshop Blend Mode Killer App

Subtractive Color Mixing using Multiply, Difference and Exclusion

The Component Blend Modes

• Hue
• Saturation
• Color
• Luminosity

The Miscellaneous Blend Modes

• Divide

Transparency Mapping and Matte Lines
Compositing Premultiplied 3D CG in Photoshop

• Unmult

Transparency Mapping and Matte Lines
Compositing Premultiplied 3D CG in Photoshop

Alpha Channels
Alpha Channels | premultiplied, straight and uncorrelated
Alpha Channel as a Clipping Channel
Alpha Channel as a Holdback Matte
Image Arithmetic
Blend Modes
Compositing Premultiplied 3D CG in Photoshop

Other Web Sites

SimpelFilter - Blending Modes of Photoshop & Co

You can simulate the halftone process in Photoshop by using the hard mix blend mode.

Create a custom halftone screen pattern of any kind you like. Use continuous tone grays from black to white. When you combine it with a black and white photograph using the hard mix blend mode, the grays will interact to force each other to black or white in the appropriate proportions.

A blurred checkerboard makes a nice basis for a halftone screen pattern.

I used twirl on the halftone screen before hard mixing it with the photo.

A hard mix with 50% gray is pixel-identical to a threshold adjustment layer at 127. You can perfectly duplicate the behavior of the threshold adjustment layer by varying the gray value with which you hard mix a photo layer.

UPDATE 6/13/2009

Use the hard mix blend mode to combine a black and white rendering of a 3D object with the same object texture mapped in closely-spaced wrapping stripes or dots and you'd have a halfway decent stab at rudimentary non-photorealistic digital engraving.

UPDATE 6/21/2009

Stochastic Halftones using the Photoshop Dissolve Blend Mode

The Served is a family of sites that brings you a steady supply of top quality creative work in specific categories: Fashion, Industrial Design, Photography, Typography, and Motion Graphics.

A brief look at two methods of combing colors - additive color, which uses red, green and blue as primaries, and so-called 'subtractive' color, which uses cyan, magenta and yellow.

Additive color describes the way colored light combines.

'Subtractive' color describes the way colored filters stack up, or the way certain pigments mix.

We usually teach children the 'subtractive' method, which uses cyan, magenta and yellow, first. We often simplify and approximate magenta as 'red' and cyan as 'blue,' so most school children think the paint primaries are red, yellow and blue.

Why do I keep putting the word 'subtractive' in quotes? Watch the clip and you'll know in 3 minutes from now.

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There are actually two kinds of 'subtractive' color mixing. One, described above, is multiplicative. The other, described here, is closer to averaging.