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Understanding the GIF file format and its settings

From: Illustrator CS5 for Web and Interactive Design

Video: Understanding the GIF file format and its settings

One of the file formats that's been around for the longest time when it comes to web design is the GIF format. In reality, some people refer to it as a GIF format. But no matter how you pronounce it, it's really the same thing. It's a file format that's actually best used for graphics that have flat color. Things like logos, for example. Now in this page now that I'm looking at right now in this file called page_designs.ai, I have two main areas of graphics that I want to kind of focus on, when we start discussing the different types of file formats that you can use.

Understanding the GIF file format and its settings

One of the file formats that's been around for the longest time when it comes to web design is the GIF format. In reality, some people refer to it as a GIF format. But no matter how you pronounce it, it's really the same thing. It's a file format that's actually best used for graphics that have flat color. Things like logos, for example. Now in this page now that I'm looking at right now in this file called page_designs.ai, I have two main areas of graphics that I want to kind of focus on, when we start discussing the different types of file formats that you can use.

We have this logo over here, which uses the flat color. Then we have a photograph over here as well. So let's explore some of these settings that we have when we start using the GIF file format. So I'm going to go to the File menu here. I'm going to choose Save for Web & Devices. I'm going to zoom out just a little bit with my magnifying glass here. So I'm just going to Option+Click on the screen here, or Alt on Windows, just so that we can kind of get a better idea of what we're looking at here for the logo here and the image itself. I'm going to take my Slice Select tool.

I'm going to click on this image right here and hold down my Shift key. Click on this image. So now these two are selected. I'll make sure that the GIF file format here is actually chosen. Now there are few important things to note about the GIF file format. The first thing is that it's actually using something that we call index color. There is a maximum of 256 colors that you can use inside of a GIF file. Now we're not talking about web safe colors here at all. You can actually mix and match any colors that you want. But a single GIF file can only contain a maximum of 256 colors.

In fact, this is the primary reason why it doesn't really work that well for images. That's because images normally have more than 256 colors, especially when you have images with lots of detail inside of it. However, when you're dealing with objects, for example, like this logo over here, there are a finite number of colors. We can starts to actually dial in those specific colors when thinking about saving the files a GIF. Now as we had discussed before, we always want to make sure that our file looks great on a computer screen, but at the same time, in the back of our minds, we always want to make sure that that file is going to be as small as possible.

Now, because a GIF file can contain a maximum of 256 colors, it doesn't mean you need to have all of those 256 colors. In fact, the fewer number of colors that you store inside of the GIF file, the smaller the file size of that GIF file. So, for example, if I want to reduce the number of colors here from 256 down to maybe 32, for example, you can start to see if I zoom in here on the image, that this image is really starting to look a little bit choppy, or you can say dithered. Let me go ahead and change to my Hand tool here.

You can see over here in the sky, we're starting to see some artifacts or detail. However, if I kind of move here to the logo itself, it still looks nice, clean, and sharp. In fact, if I go here back to this one and I change it back to maybe 16 colors, or let's do something a little bit extreme and go to 8 colors, I can really start to see what's the difference between my original nice clean image over here and how these dots are starting to appear, the dithering pattern, which really makes the image look not so hot. However, again, even though I've gone down to 8 colors, if I look at this file over here, I can see this dithering in some of the colors, but some of the colors appear solid.

So I would go to maybe something like 16 colors, or maybe 32 colors. Now I'd really start to see that the image itself is still looking great. So now that I better understood exactly what types of images or artwork I would use for the GIF file format, let's focus on actually getting all of the settings correct for this image. So the first thing I'm going to do is I'm going to use my Slice Select tool here. I'm just going to click in any other slice over here without holding down the Shift key. Then I'm going to click on this one to select just this one slice. I only want to work with this slice right here.

Next, I'm going to switch to my 2-Up view. In this way, I can really compare what my original looks like, and what my final GIF file is going to look like. I use my magnifying glass here to zoom in just a little bit more. Let's position it right here on the screen. Beautiful! So now, I'm actually going to click on this one right here. This is the GIF file that I'm working with. You can see that right now, if I use 32 colors, my file is going to be about seven-and-a-half K, which is not bad. There is still some choppiness over here inside of the art itself, so I'm going to up to around 64 colors.

You see how now I have things smoothed out just a little bit, and I'm pretty happy with what that artwork looks like now with this file size. I only went up to about eight-and-a-quarter K. Now if you take a look at the Color Table over here, Illustrator is identifying to me which colors it's actually using or storing inside of that file. Now remember my original file may have used a lot of different colors. It's now being reduced to only use 64 colors here. Keep in mind by the way, if you take a quick look at this file, it doesn't look like it has 64 colors inside of it, right? However, you have to keep in mind the anti-aliasing, the borders where one color matches up against another color.

The anti-aliasing softens those edges by blurring the edges and somehow mixing those colors. That means that really there are additional colors that are being introduced into this file. Now the method that Illustrator uses to actually reduce the number of colors in a file can be something that you can control. By default, Illustrator uses something called a selective color method. In other words, it's trying to use the colors that already exist in the image. However, there are other things that you can use as well. For example, Perceptual and Adaptive. The Restrictive one actually only uses web safe colors.

You can actually see that here inside of the Color Table; all of the colors listed here have little white diamonds inside of them, which indicate that those are web safe colors. However, I'm really seeing a lot of dithering going on over here. What I can do is come over here and choose No Dither. This way I'm basically taking my original artwork and having Illustrator snap to the closest possible web safe color. So you'll see a slight shift in color, for example, between this color of the ground over here and what I'm seeing over here, same thing over here with these colors. So the colors are not exact, but I'm not worried about getting that dithering.

Nine times out of ten though, I'm going to use the setting that Illustrator chooses, which is the Selective color method, because that usually gives me the best results. It actually keeps the original images or the original colors that are used in that file. Now one the most unique things about working with the GIF files is that they have the ability to have transparency inside of them. However, the transparency it uses it something called one bit transparency. That means that we are able to take one color in our file, and we're able to specify that that one color should become transparent.

Now, for example, if I wanted to put this logo on a colored background and I wanted the color of the background to kind of show through in the sky area over here, which right now is set to white, what I can do is set the white to be transparent. Now the way that you can do that is first to make sure that Transparency is now checked here. Then you would come down to the Color Table. Select a color that you want to be transparent. In this case, it is going to be white. Then you can click on the Transparency button right over here. Notice now that when it exports, that white area will now be exported as transparent.

Keep in mind, however, that this file originally had a white background, which means that the anti-aliasing that was applied would kind of give you a little bit of a transition between whatever solid color this is, and changing to white. In other words, if I put this on a really dark background, I might see some white fringing that happens around the edge of the graphics. To help solve that problem, you can specify something called a matte. You can see over here, there is a setting for Matte. If I click on this, I can choose that my matte be white or black, or I can choose an eyedropper color.

So, for example, if were to go now to take my Eyedropper tool, and maybe click on the sun color right over here by choosing Matte > Eyedropper Color, I am now specifying that the anti-aliasing should always transition to that color. This way I wouldn't see white fringing around the artwork itself. I would see the colors of the sun in that case. Perhaps more importantly, if you know in advance the color that this is going to be mapped against, for example, I know this is going on a web site that's going to have a dark blue background, the best thing to do would actually be to set you matte color to that dark blue color, the exact color of your background.

In that case, the colors that are here in the anti-aliasing will blend perfectly into that background. In fact, it's probably the best use for the Matte color. But I'm going to turn that off now. I'm going to set it None. You can also choose an option here called Interlaced. What Interlaced basically allows you to do is it allows the file to load in several steps inside of the web browser. It's really is far more important for larger images, ones that have larger file size that may take time to load. When you have the Interlaced option checked, the image first appears at a very low-res quality inside of the browser.

Then each pass, the image kind of rises up to full resolutions so you can now see it. It doesn't make the image to load any faster, but the person who is viewing the web site gets a really good idea about what content is on the web site. So they don't have to wait a really long time just to find out that's not what they're interested in. Now I will point out one other thing here. Notice that because I made that white transparent, the text that reads California also became transparent, because once I specified white as the transparency color, no matter where that white appears, even for example in the girls' hair and in her helmet, that part becomes transparent as well.

There is a way to get around this. The trick that many web designers use is if they know that a color is going to be transparent, they actually use a color in their design inside of Illustrator on the artboard, by using some kind of garish kind of color, like maybe a really bright blue or a bright red. Then when they come into the Save for Web & Devices dialog box, they take that bright red and they make that transparent. In other words, they are not using white as transparent. They're using some other kind of color that they would have never ever used inside of their design, and they specify that one to be transparent.

Just remember that in those cases you really want to make sure that you're using a matte, so that you don't see fringes of that bright color around the edges of your artwork. So these are the settings now that you would use for a GIF file format. Again, it's probably best to use GIF files for things like logos, text, or things that have lots of flat color. You'll get perfect colors and you'll get really small file sizes.

Show transcript

This video is part of

Image for Illustrator CS5 for Web and Interactive Design
Illustrator CS5 for Web and Interactive Design

74 video lessons · 23926 viewers

Mordy Golding
Author

 
Expand all | Collapse all
  1. 6m 56s
    1. Welcome
      1m 33s
    2. Choosing Illustrator for web and interactive design
      2m 54s
    3. Illustrator and the web design workflow
      2m 7s
    4. Using the exercise files
      22s
  2. 40m 9s
    1. Pixel dimension vs. resolution
      4m 14s
    2. Pixel Preview mode and anti-aliasing
      5m 39s
    3. Taking charge of anti-aliasing
      5m 27s
    4. Choosing the right color management settings
      7m 25s
    5. Setting up important preferences
      6m 22s
    6. Setting up a workspace optimized for web design
      11m 2s
  3. 54m 5s
    1. Using the Web document profile
      3m 39s
    2. Creating custom document profiles
      9m 38s
    3. Using Illustrator's free web templates
      2m 33s
    4. Creating a sitemap or wireframe
      2m 50s
    5. Setting up an entire web site
      9m 33s
    6. Setting up a grid
      10m 37s
    7. Setting up an online ad campaign
      8m 13s
    8. Setting up icons for iOS
      2m 24s
    9. Setting up mobile content with Adobe Device Central
      4m 38s
  4. 32m 22s
    1. Understanding web-safe colors
      11m 50s
    2. Limiting the Color Guide to web-safe colors
      4m 53s
    3. Using Recolor Art to convert art to web-safe colors
      4m 54s
    4. Getting color inspiration from Adobe Kuler
      6m 48s
    5. Using Recolor Artwork to modify colors across a site
      3m 57s
  5. 56m 54s
    1. Using the Save for Web & Devices feature
      6m 44s
    2. Understanding the GIF file format and its settings
      10m 20s
    3. Understanding the JPEG file format and its settings
      7m 39s
    4. Understanding the PNG file format and its settings
      3m 21s
    5. Understanding the WBMP file format and its settings
      1m 18s
    6. Understanding the SWF file format and its settings
      4m 13s
    7. Understanding the SVG file format and its settings
      3m 41s
    8. Adjusting the dimensions of a graphic
      4m 46s
    9. Optimizing files to a specific file size
      4m 5s
    10. Modifying Save for Web & Devices output settings
      6m 51s
    11. Previewing content in Adobe Device Central
      3m 56s
  6. 56m 6s
    1. Setting point type in Illustrator
      4m 11s
    2. Setting area type in Illustrator
      5m 20s
    3. Formatting text quickly with paragraph styles
      14m 39s
    4. Overriding formatting with character styles
      3m 2s
    5. Controlling text anti-aliasing
      4m 50s
    6. Simulating the CSS box model
      11m 14s
    7. Adding cool reflections to text and graphics
      8m 26s
    8. Applying settings quickly with Graphic Styles
      4m 24s
  7. 35m 56s
    1. Understanding the concept of slicing
      3m 22s
    2. Creating slices manually
      4m 26s
    3. Creating slices from guides
      2m 45s
    4. Creating slices from objects
      7m 33s
    5. Understanding the different slice types
      4m 20s
    6. Applying settings to slices
      9m 20s
    7. Creating hotspots with image maps
      4m 10s
  8. 23m 35s
    1. Exporting static SWF files from Illustrator
      3m 35s
    2. Animated SWF: Converting Illustrator layers to SWF frames
      4m 3s
    3. Animated SWF: Using blends to define motion
      8m 35s
    4. Animated SWF: Adding static artwork to an animation
      3m 24s
    5. Animated SWF: Controlling time within an animation
      3m 58s
  9. 17m 13s
    1. Preserving slices and structure with PSD export
      6m 10s
    2. Working with Photoshop Smart Objects
      4m 35s
    3. Sharing color swatches between Illustrator and Photoshop
      2m 52s
    4. Generating an animated GIF file with Photoshop
      3m 36s
  10. 7m 28s
    1. Exporting HTML from Illustrator for use in Dreamweaver
      3m 31s
    2. Exporting CSS and DIVs from an Illustrator layout
      3m 57s
  11. 12m 37s
    1. Moving art between Illustrator and Fireworks
      6m 25s
    2. Using dynamic shapes from Fireworks
      3m 48s
    3. Sharing color swatches between Illustrator and Fireworks
      2m 24s
  12. 16m 7s
    1. Building files for use in Flash Catalyst
      4m 28s
    2. Creating a new Flash Catalyst project from an Illustrator file
      3m 40s
    3. Copying and pasting artwork between Illustrator and Flash Catalyst
      2m 4s
    4. Roundtrip editing between Illustrator and Flash Catalyst
      3m 36s
    5. Creating Flex skins for use in Flash Builder
      2m 19s
  13. 19m 48s
    1. Understanding symbols: The lifeblood of Flash
      4m 58s
    2. Symbols: Understanding 9-slice scaling
      4m 18s
    3. Setting text that will be used in Flash Professional
      3m 5s
    4. Moving artwork between Illustrator and Flash Professional
      7m 27s
  14. 1m 6s
    1. Goodbye
      1m 6s

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