The application cuts a rectangle out of a BMP file with an image, rotates this rectangle 90 degrees clockwise and saves the result to a separate file.

All images (the original read and the saved result) are stored in the specified format:

• The general format is BMP.
• The DIB format with header BITMAPINFOHEADER (version 3) is used within the BMP format.
• The value of the biHeight field (image height) is strictly greater than zero.
• 24 bits of color per pixel are used (one byte per color channel).
• Palette (color table) is not used.
• No compression is used.

Console Application

The application is started with the following command:

./hw-01_bmp crop-rotate 'in-bmp' 'out-bmp' 'x' 'y' 'w' 'h'

Parameters used:

• crop-rotate - mandatory parameter indicating the action to be performed.
• in-bmp - name of the input file with the image.
• out-bmp - name of the output file with the image.
• x, y - coordinates of the upper left corner of the area to be cut and rotated. The coordinates start from zero, so (0, 0) is the upper left corner.
• w, h are, respectively, the width and height of the area before rotation.

Thus, if we denote the width and height of the original image by W and H, respectively, the following inequalities are true for the correct arguments:

• 0 <= x < x + w <= W
• 0 <= y < y + h <= H.

In addition to the crop-rotate command, there are the insert and extract commands, that allow you to hide a message inside the image (steganography). The insert command stores the message in the image and extract command extracts it from there.

Encoding the message

The original message consists only of capital Latin letters, a space, a period, and a comma.

To send the message, in addition to the carrier image, you need a key - a text file, which describes in which pixels the bits of the message are encoded. This file records on separate lines:

• The x and y coordinates (0 <= x < W, 0 <= y < H) of the pixel in which the the corresponding bit.
• The letter R/G/B denotes the color channel in whose low-order bit the messages.

Console application.

To save the secret line to an image, the application is started with the following command:

./hw-01_bmp insert 'in-bmp' 'out-bmp' 'key-txt' 'msg-txt'

To extract the secret string from the image, the application is started with the following command: ``:

./hw-01_bmp extract 'in-bmp' 'key-txt' 'msg-txt'

Parameters used:

• in-bmp - the name of the input file with the image.
• out-bmp - name of the output file with the image.
• key-txt - test file with a key.
• msg-txt - text file with a secret message.