LAB3 --- Image Editing and Advanced Image Processing

Images are composed of pixels. Each pixel in an image has values assigned to it. Both its position in the whole image and also its colors. The image itself also has an overall size and an overall depth of pixels per unit measure.

Computer screens as of now only display 72 pixels per inch. This is relatively coarse, actually. Print is at much higher resolution. Your average laser printer produces pages at 600 dots (equivalent to pixels) per inch. Because we move from screen to print fairly often, it is worth keeping in mind that what looks normal on the screen might look grainy when printed.

The other consideration is the way that colors are described in images. Some images are what is called grayscale, and grayscale images have pixels with a grey value ranging from 0 (white) to 256 (black). Notice that it only takes one value to describe the images, so grayscale images are often smaller than other image types that require more description. Another image format is called GIF images, and in GIF images, you have a much much larger range of color definitions from 0 to over a million, each describing a color. You can actually use programs like Photoshop to also downsample colors from their original number of colors used to a much smaller number. We will do so a bit later. JPGs are another format, and they use what is called the RGB color scheme. Here each pixel has three values each ranging from 0-256, one describing a red value, one describing a green value and one describing a blue value. These are primary colors and from their mixing, another other non-primary color can be described. Finally, the descriptions above work for transmitted light (eg. what is pushed through a cathode ray tube (CRT) monitor or LED laptop monitor). Print however is reflected light - light is reflected off the object and its color comes from how light interacts with the page. Print media uses what is called CMYK standards. That stands for Cyan, Magenta, Yellow and Blac(K). White is a transmitted color, black a reflected one (kind of), so print colorings use these mixes of CMY with K. For those who work on laying out print material on computers, being able to know the colors you see on screen are true to the colors you will see on page is important.

Photoshop is probably the best single image editor out there and has had that title for as long as I can remember. It is a complex program with many many tools, but it is also easy to use for beginners. You can do a lot of image editing without being a Photoshop expert. The first tasks today are to learn about the image itself and its quality first and then do some simple manipulations of image to impress upon you how much you can already do.

GIMP (http://www.gimp.org/) is a free-ware image manipulation program that has some of the features of Photoshop. If you can’t afford Photoshop, GIMP is a reasonable alternative.

GENERAL LAYOUT

Photoshop has a main window where images open, and then many other Windows that you can open or close. You may choose which Windows are open using the Window menu on the main window toolbar. The most important one is the tools Window which is almost always kept open. It is long thin window with many icons on it, each representing a tool that can be used to operate on a window. There are other windows that are often open too.

IMAGE EDITING:

1. Find any image you are interested in anywhere on the Web; it could but doesn't have to be the class picture, for example.

2. Find out what color mode the image is in. Go to the Image main menu and select Mode. One of the list of color modes should be checked. Go ahead and change the mode from either Index Color to RGB or vice versa. Do you notice any difference in the image itself? Switch from RGB to Index Color and also choose a different Palette called Local (Adaptive). You will notice that the number of colors box which has been greyed out is now open for you to change. Downsample from 256 colors to 10. How does your image change? What you have done is forced Photoshop to blend slightly different variants of color to the same color by forcing only 10 final colors.

3. Photoshop has an amazing undo and history function. You can undo many operations by going to Edit and the Undo. You can also see a full history of all the operations you have done to an image and undo a number of steps at once using the History menu. Go to Window and make sure History is checked. If it is, check and uncheck it so you can see which one it is. Look at the history menu as you do operations to understand what is does.

4. Find out the size of your image. Go to Image -> Size, and check out the Width/Height of the pixel dimensions (you can also set this in percentages). Also look at the document size and the resolution of the image. You can change any of the image dimensions here, including resolution. You cannot make an image have more detail that it already has, so changing the resolution up just increases the sampling of pixels but doesn't make the image any sharper. Try changing the size of the image in various ways. You can always undo your changes!

5. Photoshop distinguishes between the image and the canvas. At the risk of stating the obvious, the canvas is what the image sits on. Select Image -> Canvas size and change the canvas size to be higher. You will see that this creates "white space" around the image. This is very useful for many things.

6. You can also crop an image using the Crop tool. Remember the Tools Window (long and thin, lots of icons). The third one down on the left side (at least in Photoshop 7) is the crop tool. Select that tool and then use it to crop your image. You can drag more open or more closed any side of the crop rectangle to exactly delimit the amount you want to crop.

7. You can add text to your open image using the text tool, which is labeled on the tool windows with a large T. It should be on the right side, about eight icons down. Text is not "burned" into the image when written. It is instead written on top of the image in its own "layer". After writing some text onto your image, look at the layer tool (you can close it and reopen it under Windows if you don't see it). You will notice that the there is a background layer (which is the original opened image) and as well as a Text layer.

8. Photoshop has some amazing tools. Play with the following three especially....

a. The lasso tool (second one on left of tool window) allows you to "select" part of the image that you want with the lasso. Try lassoing something, cutting that section (under Edit-> Cut) and then paste it into a new layer (go to Layer menu and open a new layer and paste into the new layer.

b. The magic wand selects the color you select with it and all other colors that are like it. The width of colors that are also selected is an option you can set on the tool. The options for tools show up right underneath the main toolbar on the main window. The tolerance option is the one to set for greater or lesser amount of material that the magic wand selects.

c. The eye-dropper selects whatever color you click on in the image. You will notice two different "boxes" near the bottom of the tool menu, the foreground and background colors. When you use the eyedropper you select the foreground color and that color box is now the same color you selected.

d. The zoom tool (magnifying glass) allows you to zoom into the image for detail work that you might want to do.

ADVANCED IMAGE EDITING

1. Check out the Filters you can use in Photoshop. I almost never use filters, except for the Sharpen filters which help when an image is a bit blurry.

2. Layers. Layers are an incredibly central part to why Photoshop is so great. You really need to understand how they work, but it is also the hardest part of Photoshop. Layers allow you to have separate "image parts" that can be manipulated independently of one another. Go to the Layer Window. At the top of the window is a little circle with an arrow pointing right. Select this arrow and when the menu comes up, select New Layer. Try cutting and pasting from your current image or another image into the New Layer.

3. You are going to make an animated GIF of an animal flying or moving. To do this, you are going to basically treat each layer like a frame of a movie. Here are the step to do this:

a. Find an object you want to animate. Search the Internet for a picture of a butterfly or another object or animal that moves.

b. Try removing the "background" from the image to isolate just the animal if you can't find one that is already like that.

c.. Either make a new image with nothing in it that is the size you want (File -> New and set the image size) or increase the canvas size of the existing image to be large enough for the animation.

d. Copy and past the animal you have selected into a New Layer and position it where it looks like it belong for the next frame of the animation. You may also rotate the frame or edit the animal to make it look like it is moving.

e. Repeat number 4, copying each new version of the animal into a new frame.

f. When done, save this image as a Photoshop Image using File -> Save As

4. Now, open up the program Adobe ImageReady. There is an "Animation window" on the lower part of the workspace. Select the circle with the little arrow in it and choose "Make Frames From Layers". Now select the "Play" arrow from the bottom of the Window. You can also set the timing of the frames to be faster and slower under each of the frames (it should be set to 0 seconds as a default)

NOTE: If we have PhotoshopCS on computers, animations are done a slightly different way. We can figure it out as we go.

If you have time left over, keep exploring Photoshop