通过c++画一个像素点

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嘿克不黑 2021-06-17 11:46:14 ©著作权

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首先新建一个c++空项目，然后添加tgaimage.h和tgaimage.cpp文件，源代码如下：

tgaimage.h

#ifndef __IMAGE_H__
#define __IMAGE_H__

#include <fstream>

#pragma pack(push,1)
struct TGA_Header {
	char idlength;
	char colormaptype;
	char datatypecode;
	short colormaporigin;
	short colormaplength;
	char colormapdepth;
	short x_origin;
	short y_origin;
	short width;
	short height;
	char  bitsperpixel;
	char  imagedescriptor;
};
#pragma pack(pop)

struct TGAColor {
	unsigned char bgra[4];
	unsigned char bytespp;

	TGAColor() : bgra(), bytespp(1) {
		for (int i = 0; i < 4; i++) bgra[i] = 0;
	}

	TGAColor(unsigned char R, unsigned char G, unsigned char B, unsigned char A = 255) : bgra(), bytespp(4) {
		bgra[0] = B;
		bgra[1] = G;
		bgra[2] = R;
		bgra[3] = A;
	}

	TGAColor(unsigned char v) : bgra(), bytespp(1) {
		for (int i = 0; i < 4; i++) bgra[i] = 0;
		bgra[0] = v;
	}


	TGAColor(const unsigned char *p, unsigned char bpp) : bgra(), bytespp(bpp) {
		for (int i = 0; i < (int)bpp; i++) {
			bgra[i] = p[i];
		}
		for (int i = bpp; i < 4; i++) {
			bgra[i] = 0;
		}
	}

	unsigned char& operator[](const int i) { return bgra[i]; }

	TGAColor operator *(float intensity) const {
		TGAColor res = *this;
		intensity = (intensity > 1.f ? 1.f : (intensity < 0.f ? 0.f : intensity));
		for (int i = 0; i < 4; i++) res.bgra[i] = bgra[i] * intensity;
		return res;
	}
};

class TGAImage {
protected:
	unsigned char* data;
	int width;
	int height;
	int bytespp;

	bool   load_rle_data(std::ifstream &in);
	bool unload_rle_data(std::ofstream &out);
public:
	enum Format {
		GRAYSCALE = 1, RGB = 3, RGBA = 4
	};

	TGAImage();
	TGAImage(int w, int h, int bpp);
	TGAImage(const TGAImage &img);
	bool read_tga_file(const char *filename);
	bool write_tga_file(const char *filename, bool rle = true);
	bool flip_horizontally();
	bool flip_vertically();
	bool scale(int w, int h);
	TGAColor get(int x, int y);
	bool set(int x, int y, TGAColor &c);
	bool set(int x, int y, const TGAColor &c);
	~TGAImage();
	TGAImage & operator =(const TGAImage &img);
	int get_width();
	int get_height();
	int get_bytespp();
	unsigned char *buffer();
	void clear();
};

#endif //__IMAGE_H__

tgaimage.cpp

#include <iostream>
#include <fstream>
#include <string.h>
#include <time.h>
#include <math.h>
#include "tgaimage.h"

TGAImage::TGAImage() : data(NULL), width(0), height(0), bytespp(0) {}

TGAImage::TGAImage(int w, int h, int bpp) : data(NULL), width(w), height(h), bytespp(bpp) {
	unsigned long nbytes = width * height*bytespp;
	data = new unsigned char[nbytes];
	memset(data, 0, nbytes);
}

TGAImage::TGAImage(const TGAImage &img) : data(NULL), width(img.width), height(img.height), bytespp(img.bytespp) {
	unsigned long nbytes = width * height*bytespp;
	data = new unsigned char[nbytes];
	memcpy(data, img.data, nbytes);
}

TGAImage::~TGAImage() {
	if (data) delete[] data;
}

TGAImage & TGAImage::operator =(const TGAImage &img) {
	if (this != &img) {
		if (data) delete[] data;
		width = img.width;
		height = img.height;
		bytespp = img.bytespp;
		unsigned long nbytes = width * height*bytespp;
		data = new unsigned char[nbytes];
		memcpy(data, img.data, nbytes);
	}
	return *this;
}

bool TGAImage::read_tga_file(const char *filename) {
	if (data) delete[] data;
	data = NULL;
	std::ifstream in;
	in.open(filename, std::ios::binary);
	if (!in.is_open()) {
		std::cerr << "can't open file " << filename << "\n";
		in.close();
		return false;
	}
	TGA_Header header;
	in.read((char *)&header, sizeof(header));
	if (!in.good()) {
		in.close();
		std::cerr << "an error occured while reading the header\n";
		return false;
	}
	width = header.width;
	height = header.height;
	bytespp = header.bitsperpixel >> 3;
	if (width <= 0 || height <= 0 || (bytespp != GRAYSCALE && bytespp != RGB && bytespp != RGBA)) {
		in.close();
		std::cerr << "bad bpp (or width/height) value\n";
		return false;
	}
	unsigned long nbytes = bytespp * width*height;
	data = new unsigned char[nbytes];
	if (3 == header.datatypecode || 2 == header.datatypecode) {
		in.read((char *)data, nbytes);
		if (!in.good()) {
			in.close();
			std::cerr << "an error occured while reading the data\n";
			return false;
		}
	}
	else if (10 == header.datatypecode || 11 == header.datatypecode) {
		if (!load_rle_data(in)) {
			in.close();
			std::cerr << "an error occured while reading the data\n";
			return false;
		}
	}
	else {
		in.close();
		std::cerr << "unknown file format " << (int)header.datatypecode << "\n";
		return false;
	}
	if (!(header.imagedescriptor & 0x20)) {
		flip_vertically();
	}
	if (header.imagedescriptor & 0x10) {
		flip_horizontally();
	}
	std::cerr << width << "x" << height << "/" << bytespp * 8 << "\n";
	in.close();
	return true;
}

bool TGAImage::load_rle_data(std::ifstream &in) {
	unsigned long pixelcount = width * height;
	unsigned long currentpixel = 0;
	unsigned long currentbyte = 0;
	TGAColor colorbuffer;
	do {
		unsigned char chunkheader = 0;
		chunkheader = in.get();
		if (!in.good()) {
			std::cerr << "an error occured while reading the data\n";
			return false;
		}
		if (chunkheader < 128) {
			chunkheader++;
			for (int i = 0; i < chunkheader; i++) {
				in.read((char *)colorbuffer.bgra, bytespp);
				if (!in.good()) {
					std::cerr << "an error occured while reading the header\n";
					return false;
				}
				for (int t = 0; t < bytespp; t++)
					data[currentbyte++] = colorbuffer.bgra[t];
				currentpixel++;
				if (currentpixel > pixelcount) {
					std::cerr << "Too many pixels read\n";
					return false;
				}
			}
		}
		else {
			chunkheader -= 127;
			in.read((char *)colorbuffer.bgra, bytespp);
			if (!in.good()) {
				std::cerr << "an error occured while reading the header\n";
				return false;
			}
			for (int i = 0; i < chunkheader; i++) {
				for (int t = 0; t < bytespp; t++)
					data[currentbyte++] = colorbuffer.bgra[t];
				currentpixel++;
				if (currentpixel > pixelcount) {
					std::cerr << "Too many pixels read\n";
					return false;
				}
			}
		}
	} while (currentpixel < pixelcount);
	return true;
}

bool TGAImage::write_tga_file(const char *filename, bool rle) {
	unsigned char developer_area_ref[4] = { 0, 0, 0, 0 };
	unsigned char extension_area_ref[4] = { 0, 0, 0, 0 };
	unsigned char footer[18] = { 'T','R','U','E','V','I','S','I','O','N','-','X','F','I','L','E','.','\0' };
	std::ofstream out;
	out.open(filename, std::ios::binary);
	if (!out.is_open()) {
		std::cerr << "can't open file " << filename << "\n";
		out.close();
		return false;
	}
	TGA_Header header;
	memset((void *)&header, 0, sizeof(header));
	header.bitsperpixel = bytespp << 3;
	header.width = width;
	header.height = height;
	header.datatypecode = (bytespp == GRAYSCALE ? (rle ? 11 : 3) : (rle ? 10 : 2));
	header.imagedescriptor = 0x20; // top-left origin
	out.write((char *)&header, sizeof(header));
	if (!out.good()) {
		out.close();
		std::cerr << "can't dump the tga file\n";
		return false;
	}
	if (!rle) {
		out.write((char *)data, width*height*bytespp);
		if (!out.good()) {
			std::cerr << "can't unload raw data\n";
			out.close();
			return false;
		}
	}
	else {
		if (!unload_rle_data(out)) {
			out.close();
			std::cerr << "can't unload rle data\n";
			return false;
		}
	}
	out.write((char *)developer_area_ref, sizeof(developer_area_ref));
	if (!out.good()) {
		std::cerr << "can't dump the tga file\n";
		out.close();
		return false;
	}
	out.write((char *)extension_area_ref, sizeof(extension_area_ref));
	if (!out.good()) {
		std::cerr << "can't dump the tga file\n";
		out.close();
		return false;
	}
	out.write((char *)footer, sizeof(footer));
	if (!out.good()) {
		std::cerr << "can't dump the tga file\n";
		out.close();
		return false;
	}
	out.close();
	return true;
}

// TODO: it is not necessary to break a raw chunk for two equal pixels (for the matter of the resulting size)
bool TGAImage::unload_rle_data(std::ofstream &out) {
	const unsigned char max_chunk_length = 128;
	unsigned long npixels = width * height;
	unsigned long curpix = 0;
	while (curpix < npixels) {
		unsigned long chunkstart = curpix * bytespp;
		unsigned long curbyte = curpix * bytespp;
		unsigned char run_length = 1;
		bool raw = true;
		while (curpix + run_length < npixels && run_length < max_chunk_length) {
			bool succ_eq = true;
			for (int t = 0; succ_eq && t < bytespp; t++) {
				succ_eq = (data[curbyte + t] == data[curbyte + t + bytespp]);
			}
			curbyte += bytespp;
			if (1 == run_length) {
				raw = !succ_eq;
			}
			if (raw && succ_eq) {
				run_length--;
				break;
			}
			if (!raw && !succ_eq) {
				break;
			}
			run_length++;
		}
		curpix += run_length;
		out.put(raw ? run_length - 1 : run_length + 127);
		if (!out.good()) {
			std::cerr << "can't dump the tga file\n";
			return false;
		}
		out.write((char *)(data + chunkstart), (raw ? run_length * bytespp : bytespp));
		if (!out.good()) {
			std::cerr << "can't dump the tga file\n";
			return false;
		}
	}
	return true;
}

TGAColor TGAImage::get(int x, int y) {
	if (!data || x < 0 || y < 0 || x >= width || y >= height) {
		return TGAColor();
	}
	return TGAColor(data + (x + y * width)*bytespp, bytespp);
}

bool TGAImage::set(int x, int y, TGAColor &c) {
	if (!data || x < 0 || y < 0 || x >= width || y >= height) {
		return false;
	}
	memcpy(data + (x + y * width)*bytespp, c.bgra, bytespp);
	return true;
}

bool TGAImage::set(int x, int y, const TGAColor &c) {
	if (!data || x < 0 || y < 0 || x >= width || y >= height) {
		return false;
	}
	memcpy(data + (x + y * width)*bytespp, c.bgra, bytespp);
	return true;
}

int TGAImage::get_bytespp() {
	return bytespp;
}

int TGAImage::get_width() {
	return width;
}

int TGAImage::get_height() {
	return height;
}

bool TGAImage::flip_horizontally() {
	if (!data) return false;
	int half = width >> 1;
	for (int i = 0; i < half; i++) {
		for (int j = 0; j < height; j++) {
			TGAColor c1 = get(i, j);
			TGAColor c2 = get(width - 1 - i, j);
			set(i, j, c2);
			set(width - 1 - i, j, c1);
		}
	}
	return true;
}

bool TGAImage::flip_vertically() {
	if (!data) return false;
	unsigned long bytes_per_line = width * bytespp;
	unsigned char *line = new unsigned char[bytes_per_line];
	int half = height >> 1;
	for (int j = 0; j < half; j++) {
		unsigned long l1 = j * bytes_per_line;
		unsigned long l2 = (height - 1 - j)*bytes_per_line;
		memmove((void *)line, (void *)(data + l1), bytes_per_line);
		memmove((void *)(data + l1), (void *)(data + l2), bytes_per_line);
		memmove((void *)(data + l2), (void *)line, bytes_per_line);
	}
	delete[] line;
	return true;
}

unsigned char *TGAImage::buffer() {
	return data;
}

void TGAImage::clear() {
	memset((void *)data, 0, width*height*bytespp);
}

bool TGAImage::scale(int w, int h) {
	if (w <= 0 || h <= 0 || !data) return false;
	unsigned char *tdata = new unsigned char[w*h*bytespp];
	int nscanline = 0;
	int oscanline = 0;
	int erry = 0;
	unsigned long nlinebytes = w * bytespp;
	unsigned long olinebytes = width * bytespp;
	for (int j = 0; j < height; j++) {
		int errx = width - w;
		int nx = -bytespp;
		int ox = -bytespp;
		for (int i = 0; i < width; i++) {
			ox += bytespp;
			errx += w;
			while (errx >= (int)width) {
				errx -= width;
				nx += bytespp;
				memcpy(tdata + nscanline + nx, data + oscanline + ox, bytespp);
			}
		}
		erry += h;
		oscanline += olinebytes;
		while (erry >= (int)height) {
			if (erry >= (int)height << 1) // it means we jump over a scanline
				memcpy(tdata + nscanline + nlinebytes, tdata + nscanline, nlinebytes);
			erry -= height;
			nscanline += nlinebytes;
		}
	}
	delete[] data;
	data = tdata;
	width = w;
	height = h;
	return true;
}

然后添加一个main.cpp文件，代码如下：

#include "tgaimage.h"

const TGAColor white = TGAColor(255, 255, 255, 255);
const TGAColor red = TGAColor(255, 0, 0, 255);
int main(int argc, char** argv) {
	TGAImage image(100, 100, TGAImage::RGB);
	image.set(52, 41, red);
	image.flip_vertically(); // i want to have the origin at the left bottom corner of the image
	image.write_tga_file("output.tga"); 
		return 0;
}

可以发现在自己的项目文件夹下生成了一个output.tga文件。

通过c++画一个像素点_编程开发