Thursday, July 31, 2008

Gaussian Blur

On another blog, I wrote a post about Gaussian blur and what it actually means. This is a pretty widely used function in Photoshop, so I thought it would be useful to describe what's actually going on at the pixel level. Rather than repeat all this, I'll just include the link:

That other blog, by the way, was sort of a precursor to this one, so I may refer to it from time to time, but more often, I'll rewrite and repost any good stuff here.

Wednesday, July 30, 2008

More on Images and Signals

In Images as Signals, I tried to show how an image like this:

could be thought of as a signal of lightness ... a measure of how light each pixel is. I also drew a graph like this:

of that signal. Each of the ramps in that graph is one horizontal row of pixels, read from left to right (darker to lighter). So if you think about two pixels next to each other on the same row, their lightness measurements on the signal might be like this:

In other words, the pixel to the left, which is slightly darker, occurs in the signal just before the slightly lighter pixel to the right of it.

If, on the other hand, we want to locate two pixels, one above the other, with the same lightness, their positions on the signal might look like this:

What To Talk About

A while ago, I was thinking of writing a book on technology for artists. I was going to try to describe, in artist's terms, how the underlying technology of things like Photoshop, Premier, etc. work. It wasn't going to be a "How to ..." book. There are already plenty of those. It was intended as more of a general course in technology to give a basic understanding that would help in using any hardware or software.

This discussion is more general. I'm hoping it's not just for artists, but for anyone interested in how art and technology play together. I'll be happy to share what I know about the engineering side of digital art tools, but I'm also hoping to present my ideas about some broader topics like aesthetics, art as signals, etc. Most of all, I'd love to hear some comments and questions back, so I can learn some new ideas.

Some of the things I was going to include in that book:
  1. Basic math (in non-mathematical terms!!) for understanding digital images, video, audio, etc.
  2. How digital images work
    1. Raster images
    2. Vector images
  3. Color theory
  4. Typography
  5. Printing
  6. Video
    • Animation
  7. Audio
  8. Technology tools for learning about and understanding art
  9. Technology as inspiration ... art that's about technology
Sound interesting? Anything else we should talk about?

Impending Name Change

This is just a head's up that we'll be changing our name soon. I had wanted something to convey the idea of the convergence of art and technology, and Art Tech Fusion ( seems to do that. I apologize in advance for any delays while various DNS servers figure out what's going on.

Tuesday, July 29, 2008

New blog:

I've been thinking that Technology for Artists is kind of a dumb title. It sounds like all I want to talk about is Photoshop and Illustrator and Wacom tablets, etc.

In fact, what I'm really interested in is all of the possibilities of combining art and technology. How is technology used in making art? How is art used in making technology? How do they influence each other?

So, I started a new blog, ArtTechFusion, that is really open to all that stuff. The tech part of the name covers how engineers think about images, video, music, and all forms of digital media. There's a whole area of engineering called signal processing. It's usually taught as a very technical, mathematical discipline, but there are ideas in signal processing that can be understood visually, and can be a really interesting and informative way of looking at art.

The art in the name comes from ... well, ... art. ArtTechFusion is about art, technology, and any combination thereof.

I hope you'll come visit, ask questions, put in ideas, etc.

Images As Signals

I want to explore this idea of signals and signal processing in relation to art. Wikipedia offers this definition of signal in the context of electrical engineering:

In the physical world, any quantity measurable through time or over space can be taken as a signal.

Photoshop, for example, is filled with code that uses signal processing techniques to process images. Filters, blur, sharpening, edge enhancement, etc. all come from signal processing.

To understand this a little better, remember that a digital image is basically a grid of picture elements, or pixels, arranged in rows and columns. For example, consider this image:

If we zoom in on Cindy's (the gray cat's) right eye, it looks like this:

Each of those colored squares is one pixel. If we consider each pixel, one row at a time, starting from the upper left corner, we get a sequence of values. There's the upper left pixel, then the one to the right of that, then the one to the right of that one, etc. until we get to the upper right pixel. Then we move down one row and consider the one just under the upper left, then right, etc.

If the image were 10 pixels wide, the order in which we'd consider the pixels is given by these numbers:

In this way, the whole image can be thought of as a sequence of numbers, each representing a pixel value. That's a signal.

Consider an image that has alternating black and white vertical stripes:

If we consider just one row of pixels in this image (indicated by the red box), we can think of the signal as a graph of how much light is given off by each pixel. So the graph of the signal for this row can be thought of as looking like this:

The graph is very low where the pixels are black, because almost no light is given off. It's very high for the white pixels, which are giving off the maximum level of light.

Let's consider another example:

Again, thinking of just the row highlighted in red, the graph of the signal for this looks like this:

The light value starts out very low, and gets gradually higher as we move toward the right edge of the image. But remember that when we get to the right end of the row, we move down a row and start again at the left, so the actual signal for this image looks more like this:

Of course, there are more than three rows. This pattern keeps repeating with one diagonal for each row of pixels.

Is this making sense so far? These are simple examples, but I think they illustrate how images can be thought of as signals (and, I suppose, how signals can be drawn as graphs, which are basically images.)

Sunday, July 27, 2008

Art Signals

There's a great convergence of art and technology taking place. In a sense, it's been taking place since the beginning of human history. The mixing of paints, the making of musical instruments, and many aspects of performance have always involved technology. But the pace has quickened, and become almost frantic in recent decades.

The area of technology most widely connected with what we now consider digital art, be it graphics, animation, music, video, or other media, is what engineers call signal processing. Basically, all these art forms are represented as signals ... sequences of numbers. We'll talk more about that, but the most obvious interpretation of ArtSignals is the widespread use of technology ... of signal processing in art.

But, in another sense, technology not only enables some art forms. It inspires and directs them as well. Some art deals with technology as an explicit or implicit subject. A work created in Photoshop means something different from a similar looking work done with more traditional media. Even movies like Star Wars or WALL-E have important technology themes.

In addition, art plays a role in the creation of technology. The clearest example is the abundance of opportunities for visual designers and industrial designers in the creation of new high-tech products. In some sense, you can consider the difference between Apple and Microsoft as a difference in the priority each company gives to design.

Finally, art itself can be thought of as messages, although not always easy to interpret. Art works themselves are signals.

  1. Technology is used in the creation of art.
  2. Art is used in the creation of technology.
  3. Technology is often the subject, directly or indirectly, of art.
  4. Signal processing, and perhaps other aspects of technology, can provide one avenue for interpreting art.
I think 1, 2 and 3 are pretty evident. Number 4 is going to take some more discussion.

So I want to use this space to talk about all these things about art and technology. I'm hoping we can keep it light and conversational, and still get into some interesting ideas. Even talking about signal processing, we stick to pictures and non-geeky language.

I've worked for many years in the creation of graphics and multimedia software for art, design, animation, and education. I'll be happy to share what I know, but there's so much more I want to learn. I'm hoping to learn from you.

Thursday, July 24, 2008

Graphics Tablets

Someone once said that trying to draw with a mouse is like trying to write your name with a bar of soap. Actually, I think the bar of soap is easier, for reasons I'll get into later.

But if you're trying to create art on the computer, you have several options:
  1. Draw it on paper, and scan it in.
  2. Draw it with a mouse (or keyboard?!)
  3. Get a graphics tablet
  4. Use some other exotic device, like a trackball or a joystick or something equally weird.
Since most people are already comfortable with pencil and paper, #1 seems pretty attractive, but you still wind up using erasers to make corrections, dealing with smudging, etc., and perhaps having to erase and redraw parts of a picture if, for example, the head is too small or the hands are too big.

If you create the art on the computer originally, you can simply select and resize those parts of the drawing. You can also make a drawing in multiple layers, allowing you to try different positions for head, hands, etc. Layers also let you do something like pull in a photo and trace part of it (not stepping on anyone's copyrights, of course) or rearrange it to use as a reference.

The most pencil-and-paper like tool for working directly on the computer is the graphics tablet. Briefly, it's a flat board, usually used with a pen-like or pencil-like gadget called a stylus. There are a number of makes and models, but the best known and most popular are from a company called Wacom.

The main difference between a tablet (and stylus) and a mouse is how it positions. With a properly set-up tablet, the corners of the tablet always match the corners of your drawing area, and the center matches the center, etc. So if you pick up the stylus, move to one corner, and start drawing, you'll be drawing in the corner of your artwork on screen. Not so with a mouse. A mouse only measures movement, not position. So if you pick up the mouse and move it somewhere, it has no idea it's been moved, and will simply continue drawing where it thinks it was before.

This may sound like a subtle point, but once you get used to working with a tablet, you won't want to go back. Note, though, that it does take some getting used to. For one thing, you're probably already used to using a mouse, clumsy as it is, and those habits will need changing. Also, unlike drawing with a pencil on paper, using a tablet typically requires looking at the screen while moving the stylus. In other words, your eyes are not looking where your hands are. I don't have statistics, but from years of developing software for artists, and observing artists adopting software for the first time, I can assure you that this is pretty easy to get used to.

Not surprisingly, tablets come in different sizes, ranging from postcard size all the way up to large drafting table size. If you're shopping for one, consider how much space you have to devote to it. You probably want the tablet in front of you, between you and the screen. Since a lot of graphics software uses key sequences to vary brush sizes, etc., you'll want to be able to reach the keyboard, perhaps with your non-drawing hand off to the side.

Also consider your drawing style. If you like to make loose, sweeping strokes, you'll be much more comfortable with a bigger tablet. For some artists, trying to use a small tablet is like trying to draw a masterpiece on a Post-It note. Still others are comfortable working at small size. One advantage of larger sizes: You can place a drawing on the tablet and trace it with the stylus. I've found this very useful on a number of occassions.

Thursday, July 17, 2008

eCO - electronic copyright office

In the U.S., you can register copyright on any creative work, including writing, art, etc., once it has been set down in tangible form. In other words, you can't register just the idea, you have to actually create the work before you can register your copyright. It used to be that you had to fill out some forms, and send them, along with a copy of your work and, of course, a check, to the copyright office.

Now, finally, the U.S. Copyright Office has come up with a way to register copyrights electronically. You can fill out the form, pay by credit card, and even upload the work in almost any of the commonly used formats. There are still some formats and works that require sending a hardcopy deposit of the work, but there's a vast amount that can be processed completely electronically. You even save $10 on the fee.

There's another alternative that lets you fill out the copyright form on-line and then print it. You then mail the printed version along with your work. The printed version will include bar code data of the fields you enter, so it can be processed automatically once it's received by the office.

For more info on all of these options, check out:

Now you have no excuse for not registering!

Friday, July 11, 2008

Gaussian Blur

Ok, since I brought it up, here's the deal with Gaussian blur. First of all, any kind of blur is basically a way of mixing colors together. If we have some black pixels next to some white pixels, and we make the black ones along the edge a little lighter, and the white ones along the edge a little darker ... voila! Blur.

So the basic blur operation is to look at each pixel in turn, and mix in a little color from the surrounding pixels. Typically, we still want the pixel to be mostly its original color, but with some of the surrounding colors mixed in. We can come up with a kind of recipe for doing this .... mix so much of this color, plus so much of that color, stir ... etc. Let's look at a simple example.

Each pixel (except the ones at the edge of the image) has eight neighbors ...

like a tic-tac-toe board. So one way to make a mixing recipe is to figure out a percentage of each neighbor's color to mix into the center pixel's color. Since the left, right, top and bottom neighbors are slightly closer than the diagonal ones, let's take more color from them. So one example recipe could be
In other words, to figure out the new value for the middle pixel, we take 40 per cent of its color, plus 10 percent from each of the pixels above, below, left and right, plus 5 per cent of the diagonal ones.

So, suppose we have an image with a sharp edge where the top is black and the bottom is white, for example:

When we're modifying the black pixels just above the white area, the recipe will look like this:

So, in total, 20 per cent will be white, and 80 per cent will be black. In other words, we change each pixel in the bottom row of black pixels from 100% black to 80% black ... dark gray. Likewise, when we get to the next row, the top row of white pixels, they will go from being 100% white to 80% white ... light gray. The result

contains dark and light gray bands along what was originally a sharp edge. In effect, the edge is blurred. Notice that only the edge is affected. When you apply the recipe to one of the pixels in the middle of the black area, all its neighbors are black too, so the result will be ... black!

Of course, that's a very simple example. In practice, we'd use a recipe, called a kernel, that covers a lot more pixels, so for each pixel we're considering, we'd mix in a little color from pixels 2, 3, 4 or more away. This is what the radius setting in Photoshop's Gaussian blur function is for.

So, why's it called Gaussian? Because this kind of recipe, which could be visualized like this

is modeled on a mathematical function called a Gaussian distribution, named after the mathematician Carl Friedrich Gauss. Gauss was a brilliant guy. The story is that when one of his teacher's tried to challenge him by asking him to add all the numbers from 1 to 100, he thought about it for a moment, invented a quick way to solve this, and responded almost immediately with the answer. Of course, it's 5,050, as you knew, right?

Wednesday, July 9, 2008

A New Beginning ...

Ok, it's been a while, so let's start over again. I'm hoping to make this useful for artists, illustrators, designers, animators, etc. working with technology and the current set of tools out there. I don't claim to be an expert in all of these tools, but I have a pretty good understanding of the ideas and technologies behind them. I want to share that, because I think understanding what the tools are doing makes it easier to use the tools. I don't just mean which menu has Gaussian blur, but what is Gaussian blur. (I'll get to that.)

Some of the stuff discussed in earlier posts will reappear, in friendlier form, but I'm really hoping for comments and questions. That will drive the content.