hello. i need some help with BMP images.
i declared 3 structures
now i try to open the file and read from itCode:struct bmp_fileheader {...} struct bmp_infoheader {....} struct bmp_bitmap { int blue; int green; int red; };
unfortuantely i receive "segmentation fault". why?Code:FILE *captcha =fopen("captcha.bmp", "rt"); struct bmp_fileheader info; //i named my struct "info" fread(&info, 14, 1, captcha);
Your fread call should be:
You should not hardcode the size.Code:fread(&info, sizeof(info), 1, captcha);
Also, "rt" is an unusual file open mode. Perhaps you meant "r+"?
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
You should open the file in binary mode, "rb".
You should test that the file opened (a likely cause of your current trouble) :
You need to either make sure your structs are packed (and that you used explicitly-sized integers) or read the members one by one. It is more portable to read them one by one.Code:if (!captcha) { perror("fopen"); exit(EXIT_FAILURE); }
Code:#define READ(f,x) fread(&(x), 1, sizeof(x), f) typedef struct Head { int32_t size; // include <inttypes.h> for int32_t and PRNd32 int16_t planes; } Head; Head h; READ(f, h.size); READ(f, h.planes);
Last edited by john.c; 01-10-2018 at 11:42 AM.
A little inaccuracy saves tons of explanation. - H.H. Munro
"t" in the mode string is a Microsoft extension, meaning "text" or "translated" mode.
A bitmap file is not a text file, so it should be opened with the mode "rb".
