Graphics File Formats
By Tor Norbye on Jul 30, 2005
I get screenshots every now and then in the mail, and frequently in bad formats, so perhaps the following is not known to all:
- Do NOT send BMP files! They are uncompressed. A simple screenshot, which should be a something like a 50k gif, will be a 5 megabyte attachment - 100 times larger than necessary! Unfortunately, BMP is what you get by default when you grab screenshots with Ctrl-Printscreen in Windows and paste it from the clipboard. TIFF, common on the Mac, suffers from a similar bloated file size problem since it too typically is not compressed.
- Do NOT use JPEG for screenshots! Unless all compression is turned off (which it never seems to be), JPEG is a spectacularly bad format for uniform color surfaces like those you get from application screenshots. JPEG is great for photos - much better than GIF or PNG. But for screenshots it introduces all kinds of ugly visual artifacts.
...and finally, a related issue: If you're going to show a scaled down version of a picture in a web page (e.g. a thumbnail), don't just use the width and height attributes on the image tag! Not only does that require the full image to be downloaded anyway, but worse yet, most browsers do a horrible job scaling pictures. Prescale the picture in an image editor instead.