File Size

Flash is known for publishing animations that do not take up a lot of file space. The vector format of the Flash SWF file is ideal for the Web because it uses math instead of actual images to store animation elements. A 1 minute SWF will usually be smaller in file size than a 1 minute GIF image because of the use of math!

With all of the size reducing capabilities of Flash, you will still come across bloated animations on the Web. The animations that contain a BMP image of their background, the full soundtrack of Final Fantasy as the background music, and anything else the animators could get their hands on.

This tutorial will address how to reduce the file size for your movies. You will learn how to compress images, customize sound, use vectorized graphics, use fonts, and more.

Compressing Images
A nice feature of Flash is that images can be animated along with text and other objects. What is not nice about Flash, is that the default setting for optimizing and compressing images does not work for all the images all the time. The following steps explain how to optimize images individually in Flash instead of using the global image compression setting found in the Publish Settings window.

  1. Open an animation that contains several images.
  2. Go to Window | Library or press Ctrl + L. The Flash Library will appear. Find an image file and right click on it. Once the image has been right clicked, select Properties from the menu that appears. The Bitmap Properties window will appear.
  3. First, check to see if your image would look better as a GIF/PNG or JPEG. If your image has a lot of colors, use JPEG. If your image has fewer than 255 colors, use GIF/PNG. You can change the image compression type by clicking the Compression drop-down menu:

[ compression drop-down menu ]

  1. You can press the Test button to see how your image would look in the image preview box located on the top-left corner of the Bitmap Properties. To adjust the JPEG compression settings for this image, make sure you select Photo (JPEG) from the Compression drop-down menu.
  2. Uncheck the box for either Use Imported JPEG data or Use Document default quality. You will only see one of the two checkboxes displayed. Once one of the aforementioned checkboxes is unchecked, you will be provided a Quality field below the checkbox. Enter a value that you want to set the compression to. You can press the Test button to see how the image looks with the current compression setting. Best of all, when you press the Test button, you are provided with a size report on the image you just compressed:

[ size report: the image had a 98% file size reduction after compression ]

  1. You can select the Character tab from the panel and adjust the text's font, weight, size, color, and more.

The minor settings for images are often overlooked by many developers. Failing to set individual compression settings for images often creates images that are either inflated or blurry. Only by setting the compression setting for each image (provided there are only a few), can you easily judge the quality and make any necessary file size adjustments selectively.

Compressing Sound
Just like you were able to compress images individually, sounds can be compressed individually as well.

  1. Go to the Flash Library by pressing Ctrl + L or by going to Window | Library. Right click on a sound file and select Properties. The Sound Properties window will appear.
  2. Depending upon the file format of the sound file, you will see different options in your Sound Properties window. If you imported a WAV file, click the Compression drop-down menu and select a format you want to modify/save the sound as:

[ compression drop-down menu ]

  1. Select MP3 for the Compression format. MP3 formats work best for most sounds such as loops and voice-overs. For shorter sounds, ADPCM might work. Once you select MP3, you will be presented the opportunity to modify the individual properties of how your sound will export in the MP3 format:

[ compressing an MP3 file ]

Two common misconceptions that people have are that converting a bitmap image into a vector would somehow result in a smaller file. While the file size may go down, most of the time the file size increases to a level larger than that of the original image. The following section will explain how to make sure vectorized images are optimized for the best size.

Optimizing Vector Images
First of all, if you don't know how to create a vector image, this section is of little use to you. So, click the following link to learn how to convert a bitmap image into a vector:

The following tips will help you to optimize vectorized graphics so that they take up as little space as possible:

  1. Once your bitmap has been vectorized, use the Straighten or Smooth button from the Toolbox on your left.
    1. Select your vectorized bitmap. Press the Smooth button to smooth out all of the curves. Press the Straighten button to straighten the curves into lines:

    [ the smooth and straighten buttons ]

    1. The more times you press each button, the more the selected effect will be applied. For example, the vectorized images found at the top of the pages have been straightened and smoothed out. You keep on pressing the Straightened or Smooth buttons until the image does not optimize and change any further.


  2. Besides optimizing your vectorized image by using the smooth and straighten buttons, you can Optimize by using Flash's Optimize function. I bet you didn't think that Flash had an optimize command did you?
  1. Select your vectorized bitmap. Go to Modify | Optimize. The Optimize Curves window will appear:

[ the optimize curves window ]

  1. You can optimize the curves in your images by modifying the settings found in the Optimize Curves window. Of course, dragging the bar to Maximum and checking the Use Multiple passes checkbox will produce the best result.

NOTE: it may take more than 3-10 minutes to optimize a vectorized image if you set the optimization settings to maximum and check the option for multiple passes.

Using Text
While you may not know it, the text you use on your animations may take up more space than the sounds and images combined! Here are some tips to reducing file size using text.

  • Never break text apart!. You can break text apart by pressing Ctrl + B, but that increases the size of your animation dramatically. The reason is, when text is not broken, it is stored in an ASCII format understood by windows and interpreted in the Flash player of the viewer.

    When you break apart text, you are converting the text into actual shapes and lines. Basically, another vectorized image. Each shape of your letter takes up a lot of space. Worst of all, optimizing the letters causes the text to become illegible. Never break text apart unless you are displaying one or two words in a cool font that no one might have.


  • The tip you will learn deals with Dynamic Text and Input Text fields. While a novice will never encounter this problem, I'll explain anyway for those who might use text fields in their animations. First, go to your Text Options tab:

[ the text options tab ]

From the Text options tab, you will see numerous buttons under the Embed fonts caption. Below is an explanation of what each option does:

Embeds the actual font outline. The text will look blurry with this setting enabled.
Embeds the outline for only uppercase letters.
Embeds the outline for only lowercase letters.
Embeds the outline for only numbers.
Embeds the outline for punctuation marks.

As you can tell, each of those buttons correspond to a method of embedding text. When the text is embedded, an actual shape outline of the text is displayed. Checking these boxes is the equivalent of breaking apart text. While you can selectively choose which types of text (numbers, punctuation, lowercase, etc.) gets embedded into the SWF file, the files size, nonetheless, increases. It is best to avoid embedding text.

This concludes this revision of this tutorial. This tutorial was written with input from several expert Flashers from the forums. I'd like to thank the following people who gave some input and tips about helping to reduce file size in Flash: thoriphes, eyezberg, suprabeener, and Mikeylzkt. You can see all of them on the forums by clicking the Message Board link below.

I hope the information helped. If you have any questions or comments, please don't hesitate to post them on the Forums. Just post your question and I, or our friendly forum helpers, will help answer it.

The following is a list of related tutorial and help resources that you may find useful:

How to use the Forums
New, Upcoming, and In-Progress Tutorials
How to Help out
Writing Tutorials
Kirupa Chinnathambi


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