Parsing code. Convert number to pixel color. What is data in images

What is data for an image? In this code, this is the number of pixels per bit color (I don’t know exactly what it's called)

TGAImage::TGAImage(const TGAImage &img) { 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); } 

but what is this data for?

The author of the article gives such a huge number to TGAColor, but how it is converted into color.

 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); } 

here are two files. 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) { 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.raw, 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.raw[t]; currentpixel++; if (currentpixel>pixelcount) { std::cerr << "Too many pixels read\n"; return false; } } } else { chunkheader -= 127; in.read((char *)colorbuffer.raw, 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.raw[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.raw, 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; } 

here is 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 { union { struct { unsigned char b, g, r, a; }; unsigned char raw[4]; unsigned int val; }; int bytespp; TGAColor() : val(0), bytespp(1) { } TGAColor(unsigned char R, unsigned char G, unsigned char B, unsigned char A=255) : b(B), g(G), r(R), a(A), bytespp(4) { } TGAColor(int v, int bpp) : val(v), bytespp(bpp) { } TGAColor(const TGAColor &c) : val(c.val), bytespp(c.bytespp) { } TGAColor(const unsigned char *p, int bpp) : val(0), bytespp(bpp) { for (int i=0; i<bpp; i++) { raw[i] = p[i]; } } TGAColor & operator =(const TGAColor &c) { if (this != &c) { bytespp = c.bytespp; val = c.val; } return *this; } }; 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); ~TGAImage(); TGAImage & operator =(const TGAImage &img); int get_width(); int get_height(); int get_bytespp(); unsigned char *buffer(); void clear(); }; #endif //__IMAGE_H__