Bitmap Storage

Bitmaps should be saved in a file that uses the established Windows format and assigned a name with the three-character .BMP extension. The established Windows format consists of a BITMAPFILEHEADER structure followed by a BITMAPINFOHEADER structure. An array of RGBQUAD structures (also called a color table) follows the BITMAPINFOHEADER structure. The color table is followed by a second array of indexes into the color table (the actual bitmap data).

The Windows format is shown in the following illustration.

The members of the BITMAPFILEHEADER structure identify the file; specify the size of the file, in bytes; and specify the offset from the first byte in the header to the first byte of bitmap data. The members of the BITMAPINFOHEADER structure specify the bitmap's width and height, in pixels; the color format (count of color planes and color bits per pixel) of the display device on which the bitmap was created; whether the bitmap data was compressed before storage and the type of compression used; the number of bytes of bitmap data; the resolution of the display device on which the bitmap was created; and the number of colors represented in the data. The RGBQUAD structures specify the RGB intensity values for each of the colors in the device's palette. The color-index array maps indices values from the RGBQUAD array to pixels in a rectangular region on the display.

The following hexadecimal output shows the contents of the file REDBRICK.BMP.

0000 42 4d 76 02 00 00 00 00 00 00 76 00 00 00 28 00

0010 00 00 20 00 00 00 20 00 00 00 01 00 04 00 00 00

0020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

0030 00 00 00 00 00 00 00 00 00 00 00 00 80 00 00 80

0040 00 00 00 80 80 00 80 00 00 00 80 00 80 00 80 80

0050 00 00 80 80 80 00 c0 c0 c0 00 00 00 ff 00 00 ff

0060 00 00 00 ff ff 00 ff 00 00 00 ff 00 ff 00 ff ff

0070 00 00 ff ff ff 00 00 00 00 00 00 00 00 00 00 00

0080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 09 00

0090 00 00 00 00 00 00 11 11 01 19 11 01 10 10 09 09

00a0 01 09 11 11 01 90 11 01 19 09 09 91 11 10 09 11

00b0 09 11 19 10 90 11 19 01 19 19 10 10 11 10 09 01

00c0 91 10 91 09 10 10 90 99 11 11 11 11 19 00 09 01

00d0 91 01 01 19 00 99 11 10 11 91 99 11 09 90 09 91

00e0 01 11 11 11 91 10 09 19 01 00 11 90 91 10 09 01

00f0 11 99 10 01 11 11 91 11 11 19 10 11 99 10 09 10

0100 01 11 11 11 19 10 11 09 09 10 19 10 10 10 09 01

0110 11 19 00 01 10 19 10 11 11 01 99 01 11 90 09 19

0120 11 91 11 91 01 11 19 10 99 00 01 19 09 10 09 19

0130 10 91 11 01 11 11 91 01 91 19 11 00 99 90 09 01

0140 01 99 19 01 91 10 19 91 91 09 11 99 11 10 09 91

0150 11 10 11 91 99 10 90 11 01 11 11 19 11 90 09 11

0160 00 19 10 11 01 11 99 99 99 99 99 99 99 99 09 99

0170 99 99 99 99 99 99 00 00 00 00 00 00 00 00 00 00

0180 00 00 00 00 00 00 90 00 00 00 00 00 00 00 00 00

0190 00 00 00 00 00 00 99 11 11 11 19 10 19 19 11 09

01a0 10 90 91 90 91 00 91 19 19 09 01 10 09 01 11 11

01b0 91 11 11 11 10 00 91 11 01 19 10 11 10 01 01 11

01c0 90 11 11 11 91 00 99 09 19 10 11 90 09 90 91 01

01d0 19 09 91 11 01 00 90 10 19 11 00 11 11 00 10 11

01e0 01 10 11 19 11 00 90 19 10 91 01 90 19 99 00 11

01f0 91 01 11 01 91 00 99 09 09 01 10 11 91 01 10 91

0200 99 11 10 90 91 00 91 11 00 10 11 01 10 19 19 09

0210 10 00 99 01 01 00 91 01 19 91 19 91 11 09 10 11

0220 00 91 00 10 90 00 99 01 11 10 09 10 10 19 09 01

0230 91 90 11 09 11 00 90 99 11 11 11 90 19 01 19 01

0240 91 01 01 19 09 00 91 10 11 91 99 09 09 90 11 91

0250 01 19 11 11 91 00 91 19 01 00 11 00 91 10 11 01

0260 11 11 10 01 11 00 99 99 99 99 99 99 99 99 99 99

0270 99 99 99 99 99 90

The following table shows the data bytes associated with the structures in a bitmap file.