Tag Archives: fat

Bitmap manipulation programs


This program creates a bitmap from a file (or device). It’s mainly used for creating a usage map of input but it can also do conversions.

You can download bitmapdd from GitHub:

$ git clone https://github.com/andmaj/bitmapdd.git

Scenario 1:

You have a file which consists of blocks of data. If a block is full of zeros than it’s free, otherwise it’s used. You want to make a bitmap from it where a bit in the file is 0 if the corresponding block is zero, otherwise it’s 1.

For example with block size set to 4:

$ bitmapdd --bs 4 --if input.dat --of output.dat


Scenerio 2:

Converting a text of zeros and ones to a binary file where every bit corresponds to one character in the original file.

$ bitmapdd --bs 1 --null 48 --if usagemap.txt --of usagemap.dat

Note: null byte has been set to 48 which is the code of character “0” in the ASCII character table. 

usagemap.txt contains text:

usagemap.dat will contain text:

Character Decimal code Binary code
0 48 00110000
@ 64 01000000
A 65 01000001


Creates a P4 type PBM image from a binary file. With this program you can visualize your binary (for example a usage map).

You can download bitmap2pbm from GitHub:

$ git clone https://github.com/andmaj/bitmap2pbm.git

How to use

For example creating an image of the first 10000 bytes of memtest binary:

$ head -c 10000 /boot/memtest86+-4.20 | bitmap2pbm --of memtest.pbm

You can view the image in Gimp.




Creates a bitmap from FAT file system free/used clusters. The bitmap is in text format so contains zero (character 48) and one (character 49) bytes.

A zero means that the cluster is free, a one means that the cluster is used.

You can download fat2bitmap from GitHub:

$ git clone https://github.com/andmaj/fat2bitmap.git

How to use

Create a usage map of FAT file system (from filesys.iso image file)

$ fat2bitmap --if filesys.iso --of usagemap.txt

Convert the result to a binary image map with bitmapdd:

$ bitmapdd --bs 1 --null 48 --if usagemap.txt --of usagemap.dat

And finally display the usage map:

$ bitmap2pbm --if usagemap.dat --of usagemap.pbm
$ gimp usagemap.pbm &

You can also do these steps with one command:

$ fat2bitmap --if filesys.iso | bitmapdd --bs 1 --null 48 | bitmap2pbm --of usagem

To create a FAT file system image file follow my guide:

Create a FAT file system image on Linux

How to create the image file

[UPDATE: 2018.12.11.]
I’m sorry for the late correction, the approval request of comments landed in the SPAM. Stefan Naumann and Wojciech Franczyk pointed out correctly:

“Hi. In the point 3 you are creating FAT filesystem on the disk image, but you should have it created only on the partition. This is corrupting the image. You can check it trying fdisk -l test.img after performing the point 3 – you will get no partitions.

To fix it we first need to map the partition to /dev:
sudo losetup –offset 1048576 -f test.img
offset value is the start sector of the partition [2048] multiplied by sector size [512] to get bytes.

And create FAT filesystem on the partition, not disk:
sudo mkfs.vfat /dev/loop0

I’m leaving the solution here because I had exactly this problem as I needed valid whole disk image (to boot it), not only the partition 🙂
Nice tutorial thought, thanks for that, It helped me. Cheers.”

  1. Create a file filled with zeros:
    $ dd if=/dev/zero of=test.img count=50 bs=1M

    This command makes a 50 MB image file. Change the “count” argument for different size.

  2. Create the partition (and partition table):
    $ fdisk test.img
    Command (m for help): o
    Building a new DOS disklabel with disk identifier 0x46ac6035.
    Command (m for help): n
    Partition type:
      p primary (0 primary, 0 extended, 4 free)
      e extended
    Select (default p): <Enter>
    Using default response p
    Partition number (1-4, default 1): <Enter>
    First sector (2048-99999, default 2048):
    Using default value 2048
    Last sector, +sectors or +size{K,M,G} (2048-99999, default 99999): <Enter>
    Using default value 99999
    Partition 1 of type Linux and of size 47.8 MiB is set
    Command (m for help): t
    Selected partition 1
    Hex code (type L to list all codes): c
    Changed type of partition 'Linux' to 'W95 FAT32 (LBA)'
    Command (m for help): w
    The partition table has been altered!
    Syncing disks
  3. Create the FAT file system in the image
    $ mkfs.vfat test.img 
    mkfs.fat 3.0.22 (2013-07-19)

 How to mount the image and copy files

  1. Create a directory for mounting
    $ sudo mkdir /mnt/test
  2. Mount the image
    $ sudo mount test.img /mnt/test

    Now you can copy/delete files in /mnt/test directory which will be written into the image file.

  3. After file operations unmount the image
    $ sudo umount /mnt/test
  4. Delete the directory
    $ sudo rmdir /mnt/test