Comparing image pixels and using mod

[translationlost]

Hello. I'm working on an assignment where I have to read a "test.gif" image and output a photonegative of that image. After that, I need to add row mod 7 to the red components and subtract col mod 11 from the green components of every pixel while checking for underflow and overflow. Next, I read the file back in and compare the difference in pixels from each image. I'm having problems with the syntax when using mod and also ostream.

I have put in comments what i'm having problems with in main.cpp

Image.h

#ifndef Image_H
#define Image_H

#include <ostream>
#include <string>
#include "ImageLib.h"
using namespace std;

class Image {
public:
	Image(string filename);
	Image(int r, int c);
	Image(const Image &object);
	~Image();

	Image operator=(const Image &);

	pixel getPixel(int, int);
	void setPixel( int row, int col, int r, int g, int b );

	void writeFile(string filename);

	bool operator==(const Image &) const;
	bool operator!=(const Image &) const;
	friend ostream & operator<<(ostream &, const Image &);

	int getWidth() const;
	int getHeight() const;

	Image invert() const;

	bool overFlow(int, int);
	bool underFlow(int, int);

private:
	image img;
	int height;
	int width;
};
#endif 

Image.cpp

#include "Image.h"
#include "ImageLib.h"

Image::Image(string filename) {
	img = ReadGIF(filename);
	height = img.rows;
	width = img.cols;
}

Image::Image(int r, int c) {
	img = CreateImage(r,c);
	height = r;
	width = c;
}

Image::Image(const Image &object) {
	if( this != &object) {
		img = CopyImage(object.img);
		height = object.height;
		width = object.width;
	}
}

Image::~Image() {
	DeallocateImage(img);
}

Image Image::operator =(const Image &object){
	if( this != &object) {
		DeallocateImage(img);
		img = CopyImage(object.img);
		height = object.height;
		width = object.width;
	}
	return *this;
}

pixel Image::getPixel(int r, int c) {
	return img.pixels[r][c];
}

void Image::setPixel(int row, int col, int r, int g, int b) {
	img.pixels[row][col].red = r;
	img.pixels[row][col].green = g;
	img.pixels[row][col].blue = b;
}

void Image::writeFile(std::string filename) {
	WriteGIF("output.gif", img);
}

bool Image::operator ==(const Image &object) const {
	for(int row = 0; row < height; row++) {
		for(int col = 0; col < width; col++) {
			if(img.pixels[row][col].red != object.img.pixels[row][col].red ||
				img.pixels[row][col].green != object.img.pixels[row][col].green ||
				img.pixels[row][col].blue != object.img.pixels[row][col].blue)
				return false;
		}
	}
	return true;
}

bool Image::operator !=(const Image &object) const {
	if ( *this == object )
		return false;
	else
		return true;
}

ostream& operator <<(ostream &cout, const Image &object){
	cout << "Rows:" << object.height << "\n"
		 << "Columns:" << object.width;

	return cout;
}

Image Image::invert() const {
	const int MAX = 255;
	Image newObject = *this;
	for(int row = 0; row < height; row++) {
		for(int col = 0; col < width; col++) {
			newObject.img.pixels[row][col].red = MAX - img.pixels[row][col].red;
			newObject.img.pixels[row][col].green = MAX - img.pixels[row][col].green;
			newObject.img.pixels[row][col].blue = MAX - img.pixels[row][col].blue;
		}
	}
	return newObject;
}

bool Image::overFlow(int r, int red)
{
	int x = (r % 7) + red;

	if ( x > 255)
		return true;
	else
		return false;
}

bool Image::underFlow(int c, int green)
{
	int x = green - (c % 11);

	if ( x < 0)
		return true;
	else 
		return false;
}

int Image::getHeight() const {
	return height;
}

int Image::getWidth() const {
	return width;
}

Main.cpp

#include "ImageLib.h"
#include "Image.h"
#include <iostream>

void main()
{
	Image input("test.gif");

	Image vert = input.invert();
	vert.writeFile("output.gif");
	// ostream not printing the rows and columns 
	ostream& operator<<(ostream cout, const Image vert);

	// I think I need to read the image back in?

	
	// Row Mod 7, Col mod 11 
	// SYNTAX ISSUES
	for (int row = 0; row < vert.height; row++) {
		for (int col = 0; col < vert.width; col++) {
			getPixel(row,col).blue;
	
}

[coder777]

You are aware that line 12 must be cout << vert;?

I think I need to read the image back in?

No, you have 2 independend objects 'input' and 'vert' which you can use for any operation

EDIT: Line 19/20: since 'height' and 'width' are private you can't use them directly use 'getHeight()' and 'getWidth()' instead

[translationlost]

Thank you for your help! I'll give that a try.

[translationlost]

Alright, I was able to fix a couple issues but now I'm having trouble with syntax in the for loop to mod red and green for every pixel.

Main.cpp

#include "ImageLib.h"
#include "Image.h"
#include <iostream>

void main()
{
	Image input("test.gif");

	Image vert = input.invert();
	vert.writeFile("output.gif");
	cout << vert;

	// Row Mod 7, Col mod 11 
	// SYNTAX ISSUES
	for (int row = 0; row < vert.getHeight(); row++) {
		for (int col = 0; col < vert.getWidth(); col++) {
			if (Image::overFlow(row, vert.getPixel[row][col]))
				vert.getPixel[row][col] = 255;
			else
				vert.setRed(row, col, row % 7);
}

I am getting the error:
'Image::getPixel': function call missing argument list; use '&Image::getPixel' to create a pointer to member

[coder777]

Line 17: vert.getPixel[row][col] -> vert.getPixel(row, col)
Line 18: vert.getPixel[row][col] = 255; -> vert.setPixel(row, col, 255, 255, 255);