C PGM / PPM format image editor

Author: Nichita-Adrian Bunu, 323CA Facultatea de Automatica si Calculatoare UNSTPB

Contact: nichita_adrian.bunu@stud.acs.upb.ro

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Overview

This project provides a collection of subprograms to handle image processing tasks in C. The utility allows loading, selecting, cropping, rotating, equalizing, and saving images in PGM / PPM format. It includes a histogram feature for grayscale images and efficient memory management using matrix structures.

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Features and Functionality

LOAD

The load function loads an image file specified by the user, saving the information to a provided structure:

• Frees any previously loaded file data.
• Extracts metadata like type, width, height, and max value.
• Reads pixel data into a matrix depending on the image type.
• Displays an error message if the file cannot be opened.

SELECT

The selection function selects a specified area within the image:

• Validates coordinates and displays errors for invalid selections.
• If valid, prints "Selected x0 y0 x1 y1".

SELECT_ALL

select_all selects the entire image, setting selection coordinates to cover the whole file:

• Prints "Selected ALL".

HISTOGRAM

histogram generates a histogram for a grayscale image within a specified selection:

• Validates coordinates and image type.
• Displays errors for invalid inputs.
• Calculates and displays the histogram if valid.

EQUALIZE

equalize performs histogram equalization on grayscale images to balance intensity levels:

• Applies the equalization transformation and prints "Equalize done".

ROTATE

The rotate function rotates an image or selected area:

• rotate_sel rotates a selected area.
• rotate_full rotates the entire image.
• Both versions use an intermediate matrix for efficient rotation without modifying original data.

CROP

The crop function cuts out a selected portion of the image:

• Allocates a temporary matrix to store the cropped area.
• Replaces the original matrix with the cropped section.

APPLY

apply is a transformation function for image processing:

• For grayscale images, it performs a specific operation based on the parameters.
• Results are clamped to fit within allowed pixel values.

SAVE

save writes the image to a file in binary or text format based on user input:

• Writes image metadata and pixel data accordingly.

MAIN

The main function continuously processes user commands:

• Commands like LOAD, SAVE, EXIT call relevant functions.
• Frees memory upon exit and displays appropriate messages for invalid commands.

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Efficiency Enhancements

• Use of union for efficient memory management.
• Efficient memory use by managing matrix selection coordinates instead of creating full copies.
• Rotation functions skip 360-degree rotations for time efficiency.
• Explicit function and variable names contribute to maintainability and readability.

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