Hello, The FLTK functions are only allowing the complete loading of a png.
A while ago, i submitted the question of decoding an image which was already loaded in memory. I use large resources files, and i can't use the FLTK legacy functions (all my images are in the same file). So i wrote this, and post it here as there may be people interested. It works only for PNG files, but i guess it's better than nothing. You can compile it directly, you only need a png file for testing :) For the png part; i used most of the FLTK code. /* Decoding a PNG file loaded in memory. Last modification: 9 juin 2007 windows: g++ jseb.cxx $(fltk-config --cflags --ldflags) -lfltk_png - lfltk_z -lfltk_images linux: same as above, but you have to just indicate this library "- lfltk_images" */ #include <FL/Fl.H> #include <FL/Fl_Image.H> #include <stdio.h> //#include <config.h> #include <png.h> #include "zlib.h" static void png_read_data_from_mem( png_structp png_ptr, //pointer on struct which contains addy on our source datas. png_bytep data, //pointer on the dest buffer we have to fill png_size_t length); //nbr of bytes to read this time struct Png_infos { char name_png[256]; int offset_png; //where we stopped last time we read the "file" unsigned char *datas_png; }; class Fl_PNG_Memory_Image : public Fl_RGB_Image { public: Fl_PNG_Memory_Image(unsigned char *buffer_png, const char *name_png); int get_png_h() { return this->h(); } int get_png_w() { return this->w(); } private: Png_infos png_infos; }; /* when we create the class, we have to pass a pointer on the beginning of the PNG file in memory we pass also the original name of the png, for error logging purpose */ Fl_PNG_Memory_Image::Fl_PNG_Memory_Image (unsigned char *buffer_png, const char *name_png): Fl_RGB_Image(0,0,0) { int i; // Looping var int channels; // Number of color channels png_structp pp; // PNG read pointer png_infop info; // PNG info pointers png_bytep *rows; // PNG row pointers //prepare the struct png_infos.offset_png=0; png_infos.datas_png = buffer_png; // Setup the PNG data structures... pp = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); info = png_create_info_struct(pp); if (setjmp(pp->jmpbuf)) { Fl::warning("PNG file \"%s\" contains errors!\n", name_png); return; } // Initialize the function pointer to the PNG read "engine"... // png_set_read_fn (pp, (png_voidp) buffer_png, png_read_data_from_mem); png_set_read_fn (pp, (png_voidp) &png_infos, png_read_data_from_mem); //TODO : implémenter png_check_sig // Get the image dimensions and convert to grayscale or RGB... png_read_info(pp, info); if (info->color_type == PNG_COLOR_TYPE_PALETTE) png_set_expand(pp); if (info->color_type & PNG_COLOR_MASK_COLOR) channels = 3; else channels = 1; if ((info->color_type & PNG_COLOR_MASK_ALPHA) || info->num_trans) channels ++; w((int)(info->width)); h((int)(info->height)); d(channels); if (info->bit_depth < 8) { png_set_packing(pp); png_set_expand(pp); } else if (info->bit_depth == 16) png_set_strip_16(pp); # if defined(HAVE_PNG_GET_VALID) && defined(HAVE_PNG_SET_TRNS_TO_ALPHA) // Handle transparency... if (png_get_valid(pp, info, PNG_INFO_tRNS)) png_set_tRNS_to_alpha(pp); # endif // HAVE_PNG_GET_VALID && HAVE_PNG_SET_TRNS_TO_ALPHA array = new uchar[w() * h() * d()]; alloc_array = 1; // Allocate pointers... rows = new png_bytep[h()]; for (i = 0; i < h(); i ++) rows[i] = (png_bytep)(array + i * w() * d()); // Read the image, handling interlacing as needed... for (i = png_set_interlace_handling(pp); i > 0; i --) png_read_rows(pp, rows, NULL, h()); #ifdef WIN32 // Some Windows graphics drivers don't honor transparency when RGB == white if (channels == 4) { // Convert RGB to 0 when alpha == 0... uchar *ptr = (uchar *)array; for (i = w() * h(); i > 0; i --, ptr += 4) if (!ptr[3]) ptr[0] = ptr[1] = ptr[2] = 0; } #endif // WIN32 // Free memory and return... delete[] rows; png_read_end(pp, info); png_destroy_read_struct(&pp, &info, NULL); } static void png_read_data_from_mem( png_structp png_ptr, //pointer on struct which contains pointer on our datas png_bytep data, //where you have to copy the sources datas for libpng computing png_size_t length) //length of datas to copy { Png_infos *pnginfo = (Png_infos *)png_get_io_ptr (png_ptr); //get the pointer on our struct unsigned char *src = &pnginfo->datas_png[pnginfo->offset_png]; /* copy data from image buffer */ memcpy (data, src, length); /* advance in the file */ pnginfo->offset_png += length; } /* HERE ends the decoding part. For testing purpose, i wrote a test program for all this stuff */ /* test program */ #include <FL/Fl_Double_Window.H> //for the test program #include <FL/Fl_PNG_Image.H> //for the test program #include <malloc.h> //for the test program class Image : public Fl_Double_Window { public: Image(int x, int y, int width, int height, const char *title, const char *filename); Image(const char *title, const char *filename); //the window will have the png size. ~Image(); virtual void draw(); private: Fl_PNG_Memory_Image *png; unsigned char *buffer_png; int load_png(const char *filename); }; /* if you want to specify size and coordinates of the window, use this constructor */ Image::Image(int x, int y, int width, int height, const char *title, const char *filename) : Fl_Double_Window ( x,y,width,height,title) { this->png=0; this->box(FL_FLAT_BOX); this->color(FL_CYAN); load_png(filename); if (buffer_png) { png = new Fl_PNG_Memory_Image(buffer_png, filename); } } /* if you want to let the widget have the size of its png, and automatic position, use this constructor */ Image::Image(const char *title, const char *filename) : Fl_Double_Window (0,0,title) { this->png=0; load_png(filename); if (buffer_png) { png = new Fl_PNG_Memory_Image(buffer_png, filename); resize(0, 0, png->get_png_w(), png->get_png_h()); } } Image::~Image() { if (png) delete png; delete buffer_png; } void Image::draw() { if (png) { //void draw(int x, int y) //Draws image (upper-left corner at x,y). This is the same as doing draw(x,y,img->w(),img->h(),0,0). png->draw(0,0); } } int Image::load_png(const char *filename) { int retour=0; FILE *hFile; hFile=fopen (filename,"rb"); if (hFile) { fseek(hFile,0,SEEK_END); int filesize=ftell(hFile); fseek(hFile,0,SEEK_SET); buffer_png=new unsigned char[filesize]; fread (buffer_png,sizeof(char),filesize,hFile); fclose(hFile); } else { fprintf(stderr,"Impossible d'ouvrir %s\n",filename); retour=-1; } return retour; } int main() { Fl::visual(FL_RGB); Image *win = new Image(100,100,640,480,"Decoding png in memory", "file.png"); Image *win_auto = new Image("Automatic resize", "file.png"); win->show(); win_auto->show(); Fl::run(); delete win; delete win_auto; return 0; }
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