c获取图片尺寸（c++读取图片并处理）

看到一个用ASP写的读取图片文件的长度、宽度的程序，感觉有点意思，于是用C++也写了一个。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 #include <iostream> #include <fstream> #include <string> using namespace std; class CImage { private: long m_Width; long m_Height; int get_extension(string fname); public: CImage() { m_Width = 0; m_Height = 0; }; void LoadImage(char* fname); long get_width() { return m_Width; }; long get_height() { return m_Height; }; }; int CImage::get_extension(string fname) { char c = fname.at(fname.length()-1); char c2 = fname.at(fname.length()-3); if ((c == 'f') && (c2 == 'g')){ // file extension name is gif return 1; }else if ((c == 'g') && (c2 == 'j')){ // file extension name is jpg return 2; }else if ((c == 'g') && (c2 == 'p')){ // file extension name is png return 3; }else if ((c == 'p') && (c2 == 'b')){ // file extension name is bmp return 4; } return 0; } void CImage::LoadImage(char *fname) { m_Width = m_Height = 0; ifstream ffin(fname, std::ios::binary); if (!ffin){ cout<<"Can not open this file."<<endl; return; } int result = get_extension(fname); char s1[2] = {0}, s2[2] = {0}; switch(result) { case 1: // gif ffin.seekg(6); ffin.read(s1, 2); ffin.read(s2, 2); m_Width = (unsigned int)(s1[1])<<8|(unsigned int)(s1[0]); m_Height = (unsigned int)(s2[1])<<8|(unsigned int)(s2[0]); break; case 2: // jpg ffin.seekg(164); ffin.read(s1, 2); ffin.read(s2, 2); m_Width = (unsigned int)(s1[1])<<8|(unsigned int)(s1[0]); m_Height = (unsigned int)(s2[1])<<8|(unsigned int)(s2[0]); break; case 3: // png ffin.seekg(17); ffin.read(s1, 2); ffin.seekg(2, std::ios::cur); ffin.read(s2, 2); m_Width = (unsigned int)(s1[1])<<8|(unsigned int)(s1[0]); m_Height = (unsigned int)(s2[1])<<8|(unsigned int)(s2[0]); break; case 4: // bmp ffin.seekg(18); ffin.read(s1, 2); ffin.seekg(2, std::ios::cur); ffin.read(s2, 2); m_Width = (unsigned int)(s1[1])<<8|(unsigned int)(s1[0]); m_Height = (unsigned int)(s2[1])<<8|(unsigned int)(s2[0]); break; default: cout<<"NO"<<endl; break; } ffin.close(); }; int main(int argc, char *argv[]) { if (argc < 2){ printf("usage: program imagefilename/n"); return 0; } CImage test; test.LoadImage(argv[1]); cout<<"width:"<<test.get_width()<<endl; cout<<"height:"<<test.get_height()<<endl; return 0; }