Thursday, October 16, 2008

Image Formats

For my Spreadsheet: Click Here

There are, as mentioned in the prompt for this post, several types of image files (.tiff, .gif, .bmp, .png, .jpg, etc.)for saving images to one's PC or the internet. The .tiff (tagged image file format) is controlled by Adobe and was one I hoped to find for my downloads, but I could not find one on a google image search. By far the most common was JPEG. It is popular for photo images as it provides a good image compression (quality) and a small file format. Another that is common is a GIF file format. GIF (Graphic Interchange Format) is similar to a bitmap and is commonly used for low-end web page graphics and icons from what I have experienced. Portable Network Graphics, or PNGs, are a high-end bitmap image commonly used to produce cleaner looking web Graphics. One site I reviewed suggested that PNGs were intended to replace the GIF format entirely. I also did not find any PNG files to download for my five images. Bitmap (bmp) files have been around for a long time and are common for wallpaper graphics or images created in programs like paint. Our self-portrait in 5 lines is an example of a bmp. Each file type comes with a different compression, the higher the compression (I believe) the better quality image one can have for the file size. Lastly bigger files are not always better, many times it depends on either the pixel size of the image, a higher pixel x pixel ratio means a "bigger" viewable image and often incorporates a larger file size, or the file save format. That said, a 500x500 pixel JPEG image will appear to be photo quality and still have a smaller file size than a BMP of the same pixel ratio. The BMP (bitmap) image will likely be lower in quality and have a much larger file size. I will mention this further in the next section whilst discussing my downloaded images.

In the five images I downloaded, the most common type was JPG. Most of the images were photos and were under 200KB. The largest file was a portrait of the historian Charles Austin Beard at 1339KB and the smallest was a GIF at 21KB. One of my images was a Hi-Definition screenshot from gameplay of Halo 3 on the Xbox 360 that had been transferred to my PC. The image type was JPG and the clarity was amazing with a file size of 299KB. As we were supposed to alter the file type from its original to BMP for this assignment, I opened the file and "Saved as" both a 24-bit BMP and a 16-bit BMP. For the 24-bit image, the screenshot only lost minimal clarity but it went from 299KB (jpg file size) to 5.93MB in size. So minimal image quality reduction but a huge jump in file size. Then, for the 16-bit version, the next one totally tanked on image quality (looked like the old EGA graphics color set)and still went from a 299KB beautiful JPG to a .98MB very poor looking BMP. Additionally, the 16-bit changed the icon from a thumbnail of the image to a default Windows picture icon. It opened automatically with Paint instead of the Windows Photo Viewer as the JPG did. So JPG has a higher compression rate and can be stored as a smaller file size. No wonder it is used for most online photo uploading sites.

Toss more words up here later,


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