How to create bitmaps

Most images scanned with a scanner or taken with a digital camera are bitmaps. Most bitmaps have been stored in some common image file format, such as:

  • jpeg
  • tiff
  • bmp
  • png
  • gif
  • raw.

Features of storing images

Before starting to process images, you should be aware of safe and unsafe routines in storing images. Some image file formats allow you to store an image losslessly but others are lossy. The examples below illustrate what this means:

Lossless storage: the image has been stored without losing image information. As a result, the quality is as good as the original, but the file size is usually fairly large.The image above is 45 kB Lossy storage: the image is stored with less image information than the original. The result is a small image with poorer quality than the original (note the faults in the image above).The image above is 17 kB
The storage quality is 70%

To store lossless images, use e.g. the file formats PNG, TIFF and BMP.

You can store lossy images with e.g. the JPEG file format. Please observe, though, that some programs will allow lossless storage with JPEG.

If you store images in a lossy way, you will save storage capacity, but do not trust the image shown by the image-processing program when you store the image. Always open the stored image with another program to make sure the quality is good enough. If an image is compressed too much when it is stored, it may include unwanted ‘packaging traces’. The following image with very poor quality and thus no use at all (it has been stored lossy with only 30 % of the image quality) will show you what the image may look like if you compress it too much!

Always remember to make sure that the quality of an image you have stored lossy is good enough for your purposes. Mostly a storage quality of about 90 % will give you a good image, but sometimes even the 90 % setting will result in poor quality.

Keep your original image files safely stored and preferably in a lossless format! Do not forget backup copying; never modify your original images, but always create a copy of the original for modifying purposes.