C++ Unfinished Image Class

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mike_g	Created : 13 October 2007 Language : Basic C++ Unfinished Image Class
An unfinised class for dealing with images. So far it only loads and saves 24bit bitmaps, but I am planning to add support for PNG, JPG, and TGA. It is not dependent on any non-standard external libraries. The image data is loaded directly to RAM, which avoids overheads when dealing with drawing surfaces. I plan on this being a part of an image filtering prog I am working on. #include <cstring> #include <cctype> #include <fstream> typedef unsigned char Uint8; typedef unsigned short Uint16; typedef unsigned int Uint32; enum ImageExtensions { NO_EXT, EXT_INVALID, BMP, JPG, PNG, TGA }; enum ImageLoad { LOAD_IMAGE_SUCCESS, LOAD_IMAGE_INVALID, LOAD_IMAGE_UNSUPPORTED_BITDEPTH }; class Image { public: Image(){w=0;h=0;pixels=NULL;} ~Image(){delete[] pixels;} bool Load(const char); bool Save(const char); int GetWidth(); int GetHeight(); Uint32* GetImage(); private: int GetExt(const char); int LoadBMP(const char); int LoadJPG(const char); int LoadPNG(const char); int LoadTGA(const char); int SaveBMP(const char); int BytesToInt(char); short BytesToShort(char); void IntToBytes(char, Uint32); void ShortToBytes(char, Uint16); int w, h; Uint32 pixels; }; //------------------------------------------------------------------// //****************** PUBLIC FUNCTIONS ************************// //------------------------------------------------------------------// bool Image::Load(const char filename) { switch(GetExt(filename)) { case NO_EXT: return false; case EXT_INVALID: return false; case BMP: LoadBMP(filename); break; case JPG: break; case PNG: break; case TGA: break; } return true; } bool Image::Save(const char* filename) { SaveBMP(filename); return 0; } int Image::GetWidth() { return w; } int Image::GetHeight() { return h; } Uint32* Image::GetImage() { return pixels; } //------------------------------------------------------------------// //******************* PRIVATE FUNCTIONS ***********************// //------------------------------------------------------------------// int Image::GetExt(const char filename) { //This function gets a file extension and checks if it is valid char ext[10]=""; char e_ptr = ext; char f_ptr = (char)filename; f_ptr = strrchr((char)filename, '.'); if(!f_ptr) return NO_EXT; //Copy The extension converting to upper case while(e_ptr++ = toupper(f_ptr++)); //Check against valid extensions if(!strcmp(ext, ".BMP")) return BMP; if(!strcmp(ext, ".JPG")) return JPG; if(!strcmp(ext, ".JPEG")) return JPG; if(!strcmp(ext, ".PNG")) return PNG; if(!strcmp(ext, ".TGA")) return TGA; if(!strcmp(ext, ".TARGA"))return TGA; return EXT_INVALID; } int Image::LoadBMP(const char* filename) { ifstream in; in.open(filename, ios::binary); if(! in.is_open()) return LOAD_IMAGE_INVALID; char bytes[4]; in.seekg(18, ios::beg); in.read(bytes, 4); w=BytesToInt(bytes); in.read(bytes, 4); h=BytesToInt(bytes); in.seekg(2, ios::cur); in.read(bytes, 2); short bpp=BytesToShort(bytes); if(bpp != 24) return LOAD_IMAGE_UNSUPPORTED_BITDEPTH; //Allocate space for image data pixels = new Uint32[wh]; Uint32 px = pixels; in.seekg(54, ios::beg); for(int y=h; y>0; y--) { for(int x=0; x<w; x++) { in.read(bytes, 3); px=((Uint8)bytes[2]<<16)+((Uint8)bytes[1]<<8)+(Uint8)bytes[0]; px++; } } in.close(); return true; } int Image::BytesToInt(char i) { return ((Uint8)i[3]<<24)+((Uint8)i[2]<<16)+((Uint8)i[1]<<8)+(Uint8)i[0]; } short Image::BytesToShort(char* i) { return ((Uint8)i[1]<<8)+(Uint8)i[0]; } int Image::SaveBMP(const char* filename) { ofstream out; out.open(filename, ios::binary); if(! out.is_open()) return 1; char bytes[4]={'B','M','B', 'M'}; //-------HEADER--------------// out.write(bytes, 2); //Write bitmap ID IntToBytes(bytes, wh3+54); out.write(bytes, 4); //Uint32 File Size In Bytes IntToBytes(bytes, 0); out.write(bytes, 4); //Uint16 reserved 1 and 2 IntToBytes(bytes, 44); out.write(bytes, 4); //Int Offset To Image Data //------- FILE INFO --------// IntToBytes(bytes, 40); out.write(bytes, 4); //Uint32 Header Size In Bytes IntToBytes(bytes, (Uint32)w); out.write(bytes, 4); //Int Image Width IntToBytes(bytes, (Uint32)h); out.write(bytes, 4); //Int Image Height ShortToBytes(bytes, 1); out.write(bytes, 2); //Unsigned Short Planes = 1 ShortToBytes(bytes, 24); out.write(bytes, 2); //Unsigend Short Bit Depth = 24 IntToBytes(bytes, 0); out.write(bytes, 4); //Unsigned Int Compression = 0 (No compression) IntToBytes(bytes, wh3); out.write(bytes, 4); //Unsigned Int Image Size In Bytes IntToBytes(bytes, 2835); out.write(bytes, 4); out.write(bytes, 4); //Int X_Res, Y_Rex (pixes per meter) IntToBytes(bytes, 0); out.write(bytes, 4); //Uint32 number of paletted colours =0 out.write(bytes, 4); //Uint32 Important colours //------ IMAGE DATA --------// Uint32 px = pixels; for(int y=h; y>0; y--) { for(int x=0; x<w; x++) { IntToBytes(bytes, px); out.write(bytes, 3); px++; } } out.close(); return 0; } void Image::IntToBytes(char* bytes, Uint32 num) { bytes[3] = num >> 24; bytes[2] = (num >> 16) & 255; bytes[1] = (num >> 8) & 255; bytes[0] = num & 255; } void Image::ShortToBytes(char* bytes, Uint16 num) { bytes[1] = num >> 8; bytes[0] = num & 255; } --v

Comments
Saturday, 13 October 2007, 17:23
JL235	I've only skimmed your code quickly, but from the looks of it you are checking the end of the file extension to see what type of image it is. You shouldn't actually do this. Instead you should open the file up and check the data inside. If I renamed my .bmp to .png then your code wouldn't work anymore becaue it would think it's a .png and not a .bmp. If you check inside instead it'll still work, like how it does with Paint, Blitz Basic and various media players with films and sound. Rename your .avi to .mpeg and Windows Media Player will give you a warning, but still play it.
Saturday, 13 October 2007, 17:30
mike_g	Yes I could add some extra sanity checking. It would only involve reading the first 2 bytes of the file. I'll probably do that along with a couple of other things, but tbh how many people are going to rename a bitmap as .png?
Saturday, 13 October 2007, 19:45
JL235	Mike_G how many people are going to rename a bitmap as .png? Idiots will, and there was a tutorial on the Blitz site that pointed out that Blitz Basic doesn't check the extension. So you can convert your images to a different format, rename it to the format used in your code and Blitz will still read and use it. Plus if you do that your code will be more robust and harder to break.
Sunday, 14 October 2007, 00:37
Agent	Mike, why don't you just use type casting instead of all those type conversion methods? e.g. in.read((char *)&w, sizeof w); --v
Sunday, 14 October 2007, 06:39
mike_g	Wow thats cool. I had to use type casting in order to get a few things to work so far, but I never would have thought of using it like that. At first it didn't seem as if it would sort out the big endian thing you get with BMP files, but I tried it and it does. Cheers. That will make my code shorter and faster

C++ Unfinished Image Class

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