CLI application to create and read Bitmap images.
Wanted to get a better understanding of how binary files worked so I created this program to create and read bitmap files. Bitmap file format is one of the simpler file formats around.
Should work on any Linux CLI, maybe Mac OS(haven't tested it), and will not probably not work in Windows CLI.
Run command
make all
To create the binary file.
Can either create or read bitmap files.
To create pass in the -m with the name of the file to create.
-m: create -l: number of pixels in length -w: number of pixels wide -c: color of image to create. (color can be either red, orange, black, white, green, or yellow)
Example: ./bin -m new.bmp -l 50 -w 50 -c red
This will create a red bitmap image 50 pixels x 50 pixels
To read a bitmap and display in ascii art use the -r flag with name of file
Example ./bin -r shovel.bmp
Like most binary file format the bitmap file format consist of header to tell what kind of file it is and other information
Header
| Hex offset | Number of bytes | Description |
|---|---|---|
| 00 | 2 bytes | file Identifier. (BM for windows Bitmap) |
| 02 | 4 bytes | Size of Bitmap |
| 06 | 2 bytes | reserved. Can be 0 |
| 08 | 2 bytes | reserved. Can be 0 |
| 0A | 4 bytes | Starting address where pixel array can be found.(where the image starts) |
Bitmap Info Header
| Hex offset | Number of bytes | Description |
|---|---|---|
| 0E | 4 bytes | size of the header |
| 12 | 4 bytes | bitmap width |
| 16 | 4 bytes | bitmap height |
| 1A | 2 bytes | number of color planes (always 1) |
| 1C | 2 bytes | Number of bits per pixels. Values could be 1, 4, 8, 16, 24, 32. I used 24 |
| 1E | 4 bytes | Compression method used (didn't used this. Just set to 0) |
| 22 | 4 bytes | image size. Size of pixel data |
| 26 | 4 bytes | horizontal resolution |
| 2A | 4 bytes | vertical resolution |
| 2E | 4 bytes | number of colors in color palette |
| 32 | 4 bytes | number of import colors used |
Pixel Data
Since I specified 24 bits for number of bits per pixel on address 1C 3 bytes were used to determine color of each pixel in RGB, since this is in little endian the bits are reversed. Blue Green then red.
Red would be 00 00 FF.
Each row needs to end in a mutliple of 4, so if the row is 3 pixels long and each pixels is 3 bytes that would give us 9 bytes. We need to add 3 bytes 00 bytes to get to 12. Otherwise the image would be appear mutli color.