Width and Height are the width and height of the image in pixels, respectively. ColorsImportant is the number of significant colors in the palette, determined by their frequency of appearance in the bitmap data; the more frequent the occurrence of Windows bitmap files color, the more important it is. General information Since BMP is a fairly simple Windows bitmap files format, its structure is pretty straightforward. Its simple RLE compression scheme is rather inefficient for complex images. The following table shows a few examples of the number of colors that can be assigned to a pixel represented by a given number of bits. Dobb's Journalvol.