How to Draw CG Pictures

Introduction
      I'm sure all of you have seen CG pictures before. CG stands for Computer Graphic. A CG picture can be considered any artwork that was created fully or partially by a compuer.
      The Japanese are the masters of the CG art world. They make some of the most incredible Computer Generated pictures that leave you astonished by their drawing ability and bewildered by their prowess with the computer. My own art style is derived from the Japanese anime/manga art style cartoons, so I decided to try my hand in figuring out how to use the computer to color my pictures.
      This tutorial was created to teach people who aren't familiar with Photoshop. I go into a lot of specific detail and give plenty of pictures to clearly diagram my steps. I'm sure there are people out there with awesome art skill (unlike me) who just don't have the knowledge to get started into CG'ing. If you do learn anything from this, shoot me an email and send me some of your pictures!
                                                                                              -Catlord

Materials Checklist for CG'ing
1. A Computer (preferrably a Pentium-100 or above)
2. A Nice Monitor (one that can do at least 800x600)
3. A Scanner (flatbed preferrable)
4. Adobe Photoshop (hopefully 5.0)
5. Drawing Paper
6. A Pencil (mechanical is nice)
7. A Thin Black Felt-Tip Pen (i use a Koh-I-Noor 1/.50)
8. A Big Fat Eraser
9. An Excess of Spare Time

Do you have all of this stuff? The only thing that might be hard to get is Adobe Photoshop. It's the most versatile graphical program out there, and can be purchased at your local software store for about $500, or from your local software pirate for free.
Don't have a flatbed scanner either? That's not a problem.. You can pick up a nice one for under $150 nowadays. I use an Epson Perfection 610 which I picked up for $120. Yes, it's worth it even if you aren't going to CG.

Step 1: Drawing Your Picture
Using your paper and a pencil, draw a line-art picture. You don't have to worry about drawing in your shading now, since we are going to shade in color later. All we want at this point is a black outlines. Once you finish drawing the picture in pencil, use the black felt-tipped pen to ink over your pencil lines.
After you have inked your picture, use the big fat eraser to wipe away any left-behind pencil outlines. You should now just be left with black line-art on paper.

Step 2: Scanning Your Picture
Take your drawing and place it into your scanner. Using the TWAIN loader in Photoshop (File -> Import -> TWAIN_32), scan in your picture. I scan with the Grayscale setting and 600ppi resolution. What you end up with is a large picture (this one came out 4310x5841) of your line-art. We need to resize the picture into something smaller, so select Image -> Image Size and resize the height to 1000.

Step 3: Turning Black Lines Into a Layer
The next step is to take the black line-art and turn it into its own seperate Layer. We need to do this, because we need to color the space that is inside the black lines without having to worry about painting over the lines themselves.
Magnify your picture to 200%, then select Image -> Adjust -> Threshold. This will turn all the greyscales into the picture into either black or white. The Threshold Level should be adjusted so that the line art is clear and black, without having too many random speckles.

Next is to turn the picture into RGB Mode so we can color it later (Image -> Mode -> RGB Color). After that, it is time to turn the black lines into a seperate Layer. Go to Select -> Color Range to bring up the color selection. If the window shows black lines on a white background, you have to use the Eyedropper tool and select a black line. This will turn the background to black and the lines to white. Adjust the Fuzziness to that the white lines are clear and bold.

It will bring you back to your picture, but you will notice all the black lines have a Selected halo around them (an animated dashed line). Make sure that your current Active Background color is white.

Go to Edit -> Cut, and that will remove the back lines. Immediate after, do Edit -> Paste to put the lines back in. You will now notice that the black lines are on Layer 1, and your Background Layer is all white.

How Layers Work

Since we are starting to use different Layers, it would be very beneficial to explain how the Layers system works in Photoshop. The Layers system is the most important concept to understand in Photoshop if you are going to be doing CG art. If you cannot find your Layers window, you have to click on the Layers tab in the bottom-right corner of the screen. If it's still not there, then goto Window -> Show Layers.

I have diagrammed the layers window so I can explain the different functions.

1. The Background Layer

2. Layer 1

3. Opacity

4. Layer Command Menu

5. Preserve Transparency

6. Hide Layer

1 - The Background Layer
      The easiest way to explain Layers is to use analogies. Consider the Background Layer to be a thick piece of white paper. You can draw on the Background Layer, you can't see through it, and it is the bottom-most layer in our Layer stack.

2 - Layer 1
      Still using analogies, consider Layer 1 to be a piece of clear plastic that is used in classroom overhead projectors. You know, that transparent wobbily plastic film that your teachers and professors wrote on with a dry-erase marker to project their lecture notes onto the wall. Right now on Layer 1, we have our black line art drawn and nothing else. Since the rest of Layer 1 is clear, we can see the Background Layer (our thick white piece of paper) underneath. If we were to add another Layer on top and above Layer 1, it would be like stacking another clear piece of plastic onto our pile. You would also notice that Layer 1 is highlighted blue. This is to indicate that this is the Active Layer. This is the Layer that you are currently editing.

3 - Opacity
      The Opacity percentage adjusts the intensity of the layer. 100% is opaque, 0% is transparent, and percentages inbetween are different degrees of translucency.

4 - Layer Commands Menu
      This has good stuff in it. Most important is New Layer, Merge Down, and Flatten Image. New Layer will create a new Layer right above the Active Layer. Merge Down will take the Active Layer and combine it will the Layer directly under it. Flatten Image will take all the Layers in the image and combine them into one layer- the Background Layer.
      IMPORTANT NOTE: In order to save your picture into either the .JPG, .GIF, or .BMP format, you have to have only one Layer in your picture- the Background Layer.

5 - Preserve Transparency
      If you have Preserve Transparency for a certain layer(s) checked, Layers below it cannot be affected through operations. Sometimes, you need the Layers to interact with one another when using certain filters like Drop Shadow.

6 - Hide Layer
      This is useful if you have too many Layers cluttering your view up. Toggling this option will hide the Layer(s) out of view. The other advantage to this option is you can merge specific Layers together by hiding certain Layers, then go into the Layer Commands Menu and selecting Merge Visible. Layers that are hidden will not be merged into the Background Layer.

How Layers Work

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