5 FAH-8 H-440
images
(CT:WEB-31; 07-10-2024)
(Office of Origin: DT/OPS)
5 FAH-8 H-441 FORMATS
(CT:WEB-26; 04-14-2023)
a. Graphics used on websites need to be compressed or reduced in size to download in a reasonable amount of time. The two standard compression formats are graphic interchange format (GIF) and Joint Photographic Experts Group (JPEG) with a third, portable network graphics (PNG), increasingly gaining acceptance. The formats addressed in this handbook are the most common but are not the only formats available for use.
b. The format selected for an image will depend on the type of image, the desired file size, and how it is displayed. If after selecting an image format the quality of the image does not meet expectations, select another format. The goal is to produce images that fulfill the objectives of the web page, not necessarily to achieve a specific image characteristic (e.g., smallest file size, most number of colors). The standard resolution for web images is 72 dpi.
c. When selecting images to use on a website, Department of State offices must conform to copyright laws.
d. Images on Intranet sites and external websites must be compliant with Section 508 of the Rehabilitation Act of 1973 and include alternative text so the text can be read by screen reading software used by people who are blind or who have low vision. The U.S. Access Board is the authority for developing guidelines and standards for Section 508 (https://www.access-board.gov).
5 FAH-8 H-441.1 Graphic Interchange Format
(CT:WEB-26; 04-14-2023)
a. GIFs works well with flat color fields that are well defined such as clip art and diagrams. GIF files are limited to 256 discrete colors but attempt to display additional hues by “dithering” or mixing pixels of two or more colors.
b. The GIF format is interlaced. Viewers can get an impression of the finished image from the rough first layer and if interested, watch as the second and third layers are added to complete the picture. GIF files can be made transparent so the background of the website will not be obscured by anything other than the image itself.
5 FAH-8 H-441.2 Joint Photographic Experts Group
(CT:WEB-26; 04-14-2023)
a. JPEG is usually best for photographs and graphics with many color fields. It does a good job of displaying complex color fields that blend and fade into each other.
b. JPEG has a higher compression factor that will result in smaller files. The JPEG image is drawn as a finished picture from top to bottom requiring the viewer to wait until it is finished to see what is displayed.
5 FAH-8 H-441.3 Portable Network Graphics
(CT:WEB-26; 04-14-2023)
a. PNG was developed as an alternative to GIF. It has a variable transparency capability and better compression than GIF. PNG supports the two JPEG image types, TrueColor and grayscale, and the GIF image type, palette-based or 8-bit. The greatest advantage of PNG is the portability feature that is achieved by a single method of implementation regardless of platform.
b. Although PNG will support TrueColor, JPEG is usually the better choice for finished TrueColor images such as photographs and diagrams.
5 FAH-8 H-441.4 Bitmap
(CT:WEB-26; 04-14-2023)
a. The bitmapped graphics format is the default for saving images in Microsoft applications. An example is using the <CTRL><PRINT SCREEN> keys to capture an image of the current display.
b. Normally, bitmapped images are not compressed, and the resulting image files will be significantly larger than compressed file formats. BMP files are not suitable for websites due to the time required to transfer the large files and should be avoided on Department of State websites.
5 FAH-8 H-442 Through H-449 Unassigned