Savy Cat

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Rotate90

Team Members

1. Evan Marinzel

Progress

Assignment 1

I kept things very simple and created a function that rotates an image 90° clockwise.

Then, I profile and evaluate performance of rotating a tiny, medium, and large sized image file 12 times each.

Dependencies

Two open-source utilities are required in order to run the project code:

CImg

Download and extract the CImg Library (Standard Package). This provides the template class used to store image information. The library contains many useful image manipulation functions and methods, including rotate, but we will only be making use of the CImg class and the Display function. Make sure your project include path can find CImg.h, which should be located in the root of the extracted files.

libjpeg

libjpeg provides the functionality of reading .jpg file data into a CImg object. It's not quite as strait forward as getting CImg, as you need to compile libjpeg from source. I used the most recent (Jan 2018) version named jpegsr9c.zip from this listing.

If you have trouble building the solution, this article on Stackoverflow helped me compile it.

Once libjpeg has been built, it should result in creation of "libjpeg.lib". Be sure to link this file with compilation of the project code.

Initial Code

Rotate.h

// Evan Marinzel - DPS915 Project
// Rotate.h

#pragma once

#define cimg_use_jpeg
#define PX_TYPE unsigned char

#include <CImg.h>
#include <iostream>
#include <iomanip>


// Indexing function for CImg object.
// CImg[x][y][z]
inline int idx(int x, int y, int w, int h, int z) {
	return x + y * w + w * h * z;
}

// Indexing function for accessing pixel location rotated 90 degrees relative to current location
// CImg[h - 1 - y][x][z]
inline int idx90(int x, int y, int w, int h, int z) {
	return (h - 1 - y) + x * h + w * h * z;
}

// Prints colour channel values of img to console.
// Opens image, mouse-over pixels to verify indexing is correct.
// Uses 40 x 40 pixel sample from the top left corner if img is larger than 40 x 40
void display(const cimg_library::CImg<PX_TYPE> img) {

	int height = img.height() > 40 ? 40 : img.height();
	int width = img.width() > 40 ? 40 : img.width();

	for (int i = 0; i < img.spectrum(); i++) {
		if (i == 0)
			std::cout << "Red:" << std::endl;
		else if (i == 1)
			std::cout << "Green:" << std::endl;
		else if (i == 2)
			std::cout << "Blue:" << std::endl;
		for (int j = 0; j < height; j++) {
			for (int k = 0; k < width; k++) {
				std::cout << std::setw(4) << (int)img[idx(k, j, img.width(), img.height(), i)];
			}
			std::cout << std::endl;
		}
		std::cout << std::endl;
	}

	cimg_library::CImg<PX_TYPE> imgCropped(img);
	imgCropped.crop(0, 0, width - 1, height - 1, 0);
	imgCropped.display();

}

// Print image dimensions and size to console.
void imgStats(const char* title, cimg_library::CImg<PX_TYPE> img) {

	std::cout << title << " Image Data" << std::endl;
	std::cout << std::setfill('=') << std::setw(strlen(title) + 11) << "=" << std::setfill(' ') << std::endl;
	std::cout << std::setw(17) << std::right << "Width: " << img.width() << "px" << std::endl;
	std::cout << std::setw(17) << std::right << "Height: " << img.height() << "px" << std::endl;
	std::cout << std::setw(17) << std::right << "Depth: " << img.depth() << std::endl;
	std::cout << std::setw(17) << std::right << "Colour Channels: " << img.spectrum() << std::endl;
	std::cout << std::setw(17) << std::right << "Pixel Size: " << sizeof(PX_TYPE) << " bytes" << std::endl;
	std::cout << std::setw(17) << std::right << "Total Size: " << img.size() << " bytes" << std::endl;
	std::cout << std::endl;

}

// Rotate src image 90 degrees clockwise.
// Works by assigning pixel values from src to dst.
//   - dst must be allocated as valid size
void rotate90(cimg_library::CImg<PX_TYPE> src, cimg_library::CImg<PX_TYPE> &dst) {

	for (int i = 0; i < src.spectrum(); i++) {
		for (int j = 0; j < src.height(); j++) {
			for (int k = 0; k < src.width(); k++)
				dst[idx90(k, j, src.width(), src.height(), i)] = src[idx(k, j, src.width(), src.height(), i)];
		}
	}

}

// Rotate image 360 degrees by calling rotate90 4 times.
void rotate90x4(cimg_library::CImg<PX_TYPE> src, cimg_library::CImg<PX_TYPE> dst) {

	rotate90(src, dst);
	rotate90(dst, src);
	rotate90(src, dst);
	rotate90(dst, src);

}