CS 330 Lecture 26 – C++ I/O, Overloading, References
Agenda
- what ?s
- the philosophy of Stroustrup
- C++ I/O
- builtin operators
- references
- const
- next up: polymorphism
TODO
- 1/4 sheet: Scour the results of the 2015 Stack Overflow Developer Survey. What’s interesting? Surprising? Devastating? Encouraging? Where do you deviate? Where do you conform?
Code
Image.h
#ifndef IMAGE_H
#define IMAGE_H
#include <iostream>
#include <string>
namespace cs330 {
class Image {
public:
Image(int width, int height);
Image(std::string path);
~Image();
int GetWidth() const;
int GetHeight() const;
unsigned char operator()(int r, int c) const;
private:
int width;
int height;
unsigned char *pixels;
};
}
std::ostream& operator<<(std::ostream &out, const cs330::Image &image);
#endif
Image.cpp
#include <fstream>
#include "Image.h"
namespace cs330 {
Image::Image(int width, int height) :
// The C++ way:
width(width),
height(height) {
// The Java way:
/* this->width = width; */
/* this->height = height; */
pixels = new unsigned char[width * height];
}
Image::Image(std::string path) {
std::ifstream in(path.c_str());
std::string wasted;
int max;
in >> wasted >> width >> height >> max;
// TODO read pixels
pixels = new unsigned char[width * height];
for (int i = 0; i < width * height; ++i) {
int igray;
in >> igray;
pixels[i] = (unsigned char) igray;
}
in.close();
}
Image::~Image() {
delete[] pixels;
}
int Image::GetWidth() const {
return width;
}
int Image::GetHeight() const {
return height;
}
unsigned char Image::operator()(int r, int c) const {
return pixels[c + r * GetWidth()];
}
}
std::ostream& operator<<(std::ostream &out, const cs330::Image &image) {
out << "P2" << std::endl;
out << image.GetWidth() << " " << image.GetHeight() << std::endl;
out << 255 << std::endl;
// write pixels
for (int r = 0; r < image.GetHeight(); ++r) {
for (int c = 0; c < image.GetWidth(); ++c) {
out << (int) image(r, c) << std::endl;
}
}
return out;
}
main.cpp
#include <iostream>
#include "Image.h"
/* using namespace cs330; */
/* using cs330::Image; */
int main(int argc, char **argv) {
cs330::Image before(argv[1]);
// do something to before
std::cout << before;
return 0;
}
Haiku
on earning the right
Try your spinach, dear
In this house we are good eaters
Or informed haters
Try your spinach, dear
In this house we are good eaters
Or informed haters