GIF

PAGE (3 of 4)

Interlaced GIFs

Interlacing

The GIF format includes an option to aid in the viewing of images as they are being downloaded. For many images Web browsers will either wait until the entire image is downloaded before displaying or slowly show the image from top to bottom, displaying the image as it is transferred. Interlaced GIF images are especially helpful to modem users.

Interlaced GIF images are stored to allow alternating lines of the image to be viewed as they are received. Every 8^th line is displayed, followed by every 4^th lines, then every 2^nd line and then the remaining lines. This provides a fading in effect for viewing of the image during transmission. The following link will allow you to view large interlaced GIF image in a separate window.

The JPEG image format supports a similar feature format: progressive JPEG. The Va Tech sports home page used to feature, (11/1/97), a non-progressive JPEG logo which should of course have been a progressive JPEG logo. In order to see the difference using a fast ethernet connection, carefully notice the out of focus initial download of the progressive JPEG.

Paint Shop Pro Interlacing

Following the previous directions launch Paint Shop Pro application if it is not currently executing. Open a saved image file in Paint Shop Pro. From the File menu, select Save As... From the Subtype: list, simply select the Version 89a Interlaced entry for GIFs. (Note - changing the Save as type: to JPG - JPEG - JFIF Compliant, gives a similar option for saving progressive JPEGs.