Bitmap Example

The image below was taken with my digital camera. It uses the jpeg file format and it is 540x405 pixels. Images from a digital cameras and scanners are always bitmap images.

Britt's Eye

The problem with bitmap images is that they are difficult to edit and resize. You can downsize the image without much effect. Here is the same image resized to 200x150 pixels with 80% compression applied.

Britt's eye small

I then opened the small image above and resized it back to 540x405 pixels.

Britt's eye enlarged

Increasing the size of the image has blurred it significantly. Notice the watermark, tinkertech.net, on the first image; it's legible. The last image the watermark cannot be read and the reflections in the eye are very blurred.

The other problem occurs when an image is resaved. If you resave an image you must be careful not to recompress the image. The act of resaving an image with additional compression will cause a loss of image quality.

For an overview of the best methods for increasing the size of an image or resampling an image review this article from About.com.

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