Perhaps you've tried your hand at designing a paper model on your computer and are pleased with the results. You can print a million copies for your own use, but what is the best way to share your creation with the rest of the world? If you post your original artwork files on the internet, chances are the majority of viewers will not have the correct program to read them. Instead you will need to save your art in a common format everyone will be able to read and print from.

In the first part of this article, we examined the differences between raster-based artwork and vector-based artwork in regards to designing a paper model. Your choice of one or the other will depend on the drawing programs you have access to, the programs you are familiar with, and the style you want for your illustration.

If you are creating your paper model in a raster paint program, you can save it in GIF or JPEG format, which are the common standards on the web and easily viewable in any browser, then saved to the viewer's desktop for printing from a paint program. If you are creating your illustration in a vector drawing program, you could also save it to bitmapped GIF or JPEG format, but as we shall see below, it is often better to preserve the drawing in vector format. First lets look at the differences between raster artwork on the web.

GIF vs. JPEG Artwork

GIF files on the internet are raster-based artwork at 72 pixels per inch. The gif format was designed to save high-resolution images at very small file sizes. The method of compression involves counting the number of colors in the file, then counting the number of pixels that repeat that color in rows across the image. This means that images made of large areas of solid colors, like the simple model shown above, or images with sharp contrasts, such as blocks of text, are ideal for the gif format.

JPEG files on the internet are also raster-based artwork at a default 72 pixels per inch. The JPEG format was designed to compress large images as well, specifically photographs. The compression works by altering pixels next to each other in small sections, removing data that the human eye does not readily notice. As you can see in the enlargement, the original colors of some of the pixels have been changed, resulting in "artifacts" such as the two gray pixels to the left of the letter F and the dark spot below the letter O. In a photograph these artifacts are rarely noticeable, but on artwork with blocks of color the artifacts are easily spotted, so for these types of artwork the JPEG format should not be used.

Image Compression and File Size

Saving your artwork for posting on the internet involves a number of tradeoffs. With both GIF and JPEG art, you can adjust the level of file compression when you save from your original art. What will result in a smaller file size ideal for downloading off the internet might also cause distortion of your artwork. On the other hand, saving an uncompressed image may create an enormous file no one will have the patience to download!

Here are some extreme examples to show the tradeoffs in quality and file size:

When you save your artwork as a GIF, adjust the color palette used to the minimum that will not noticeably change the colors of your image.

GIF: 16 colors, 8K file size

GIF: 256 colors, 24K file size

When saving as a JPEG, find a compression level that saves file space without muddying the image.

JPEG: Low quality (15), 4K file size

JPEG: High quality (100), 32K file size

In this photographic image the differences in the artwork are difficult to see. In the 16-color GIF image, notice that the bricks have become more monotone, losing the yellow tones. In the Low quality JPEG, the mortar betwen the bricks seems to have become blurry. As you can see, photographic images can be compressed with only slight distortion. How about a simple gradient fill more typical of a paper model piece:

GIF: 16 colors, 3K file size

GIF: 256 colors, 5K file size

JPEG: Low quality (15), 2K file size

JPEG: High quality (100), 8K file size

As you can see, reducing the number of colors in the GIF resulted in a stair-step banding instead of a smooth gradation, and setting the quality level at Low in the JPEG resulted in a blurry image where one of the rivets disappeared! Try saving your artwork at several different settings to get the smallest file size where the quality of the image is not degraded noticeably.

The difference in file sizes in these small examples may seem slight, perhaps negligible, but if your artwork fills a full page, the difference in file sizes you'll notice by adjusting the compression settings will be much greater.

PDF format

The other common format for sharing paper model illustrations on the internet is PDF. This format is incredibly efficient at compressing vector art and text, so if your artwork is created in a vector drawing program you will notice the best results. If you are creating your art in a vector-drawing program, there is no need to save it as a bitmapped raster file, as you will only lose the crisp lines and smooth details of the vector format.

Saving your vector artwork as raster files will increase the file size needed. As an example, a full sized page of a vector drawn illustration might be saved as a 128K PDF file, yet saving the same artwork as a 300dpi JPEG at the lowest quality setting requires 400K, and saving as GIF requires a whopping 525K!

If you have drawn your artwork in a vector-based drawing program, the last thing you want to do is to save this as a GIF or JPEG file. Even if you have combined raster and vector files in your illustration, the best file format to save the file without image distortion is Acrobat PDF, which allows you to save raster and vector images and type together without loss in quality. Saving your artwork as a PDF allows you to keep the same look to your artwork while also creating very small file sizes that are perfect for sharing over the internet.

If you are creating your illustration in a paint program, you can also save raster paint images in PDF format, which will allow you to save images at the exact size and resolution of your original art, but with all raster artwork you will confront the same compression vs. file size tradeoffs we saw when using JPEG format above. PDF uses JPEG compression for color raster images.

You can save artwork in PDF format from a number of different programs. But if you have access to Acrobat Distiller, or the full Adobe Acrobat, you'll have the most options for saving your file. You'll be able to choose the exact resolution and compression level of raster artwork. For example, the Acrobat "Screen" setting will downsample your art to screen resolution of 72dpi with Low quality JPEG compression. This is intended for documents that will be viewed on screen, not for printing. The "Print" setting will preserve your artwork at 300dpi, for documents that will be printed on inkjet or laser printers. If you have Acrobat Distiller, you can adjust the resolution and compression settings exactly to get the best balance between file size and print quality.