Load BMP? - BlitzCoder.net

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Socoder -> C/C++/C#/Other -> Load BMP?
Sun, 24 Oct 2010, 03:07
spinal	I'm trying to load a bmp, but it doesn't seem to work My C isn't all that good, can anyone see what I'm doing wrong here? void readBMP(char * filename, int buffer, int width, int height){ FILE imgFile=fopen(filename,"rb"); if(imgFile) { // read height+width fseek(imgFile,18,SEEK_SET); fread(&width, 4, 1, imgFile); fread(&height, 4, 1, imgFile); // read bit depth of image u16 bytes=0; fseek(imgFile,28,SEEK_SET); fread(&bytes, 2, 1, imgFile); fseek(imgFile,54,SEEK_SET); bytes = bytes >> 3; // read image data if(bytes==2){ // 15bit u16 x,y,t,r,g,b,h,w; h = height; w = width; for(y=0; y<h; y++){ for(x=0; x<w; x++){ fread(&t, 2, 1, imgFile); r = (t >> 10)&31; g = (t >> 5)&31; b = t&31; buffer[w*(h-y-1)] = RGB15(r,g,b); } } }// bytes==2 fclose(imgFile); }// if imgFile } --v -=-=- Check out my excellent homepage!
Sun, 24 Oct 2010, 03:37
shroom_monk	For some of the BBC BASIC things I've been doing as a side-project in my Computing lessons (and I may eventually put up here at some point), I recently wrote a BBC BASIC program to read in bitmaps (to then do some other stuff with them). Here's the bitmap reading stuff in BASIC: REM OPEN FILE CLS INPUT "NAME OF FILE", FILENAME$ IMF = OPENIN(FILENAME$) PRINT REM OBTAIN FILE INFORMATION FILETYPE$ = CHR$(BGET#IMF) + CHR$(BGET#IMF) IF(FILETYPE$ <> "BM") THEN PRINT "NOT A BITMAP!" END ENDIF FILESIZE = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "FILE SIZE: "; FILESIZE FOR I = 1 TO 4 TMP = BGET#IMF NEXT I OFFSET = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "OFFSET: "; OFFSET HEADERSIZE = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "HEADER SIZE: "; HEADERSIZE IMGW = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "WIDTH: "; IMGW IMGH = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "HEIGHT: "; IMGH PLANES = BGET#IMF + (BGET#IMF * (2^8)) PRINT "COLOUR PLANES: "; PLANES BPP = BGET#IMF + (BGET#IMF * (2^8)) PRINT "BITS PER PIXEL: "; BPP IF(BPP <> 24) THEN PRINT PRINT "24 BIT BITMAPS ONLY PLEASE!" END ENDIF COMPRESSION = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "COMPRESSION METHOD: "; COMPRESSION IMAGESIZE = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "IMAGE SIZE (RAW DATA): "; IMAGESIZE HRES = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "HORIZONTAL RESOLUTION: "; HRES VRES = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "VERTICAL RESOLUTION: "; VRES PALETTESIZE = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "COLOURS IN PALETTE: "; PALETTESIZE IMPCOLOURS = BGET#IMF + (BGET#IMF * (2^8)) + (BGET#IMF * (2^16)) + (BGET#IMF * (2^24)) PRINT "IMPORTANT COLOURS: "; IMPCOLOURS REM LOAD AND DRAW IMAGE IMAGEDATA_R = 0 IMAGEDATA_G = 0 IMAGEDATA_B = 0 DIM IMAGEBRIGHT(IMGW,IMGH) FOR H = IMGH TO 1 STEP -1 FOR W = 1 TO IMGW IMAGEDATA_R = BGET#IMF IMAGEDATA_G = BGET#IMF IMAGEDATA_B = BGET#IMF IMAGEBRIGHT(W,H) = (IMAGEDATA_R + IMAGEDATA_G + IMAGEDATA_B) / 3 NEXT W NEXT H --v That should be the bit of code that loads the image into memory. I only wanted the brightnesses of each pixel, but you can see where the colours come from. See if that helps, but I'll have a read over your code too. \|edit\| OK, I've never done C, only C++, and I really can't make heads or tails of how C manipulates files. But by the looks of things you're trying to read the width and height from the header, then skip to the byte where the image data starts? When I was researching the file type for the above program, I found that different formats of BMP can have wildly different header sizes and data starting locations. Hence the reason why my code only likes 24-bit bitmaps (to keep it simple), and why I read in each part of the header, rather than trying to skip to a certain location. You could always try that, and then ignore the useless data. \|edit\| -=-=- A mushroom a day keeps the doctor away... Keep It Simple, Shroom!
Sun, 24 Oct 2010, 04:23
Afr0	Yeah, as shroom_monk says, the header sizes vary. Always do your research properly when trying to load a fileformat! Here are the most common ones: 12 OS/2 V1 BITMAPCOREHEADER OS/2 and also all Windows versions since Windows 3.0 64 OS/2 V2 BITMAPCOREHEADER2 40 Windows V3 BITMAPINFOHEADER all Windows versions since Windows 3.0 108 Windows V4 BITMAPV4HEADER all Windows versions since Windows 95/NT4 124 Windows V5 BITMAPV5HEADER Windows 98/2000 and newer For the BMP format, you can actually find most of the information you need right at Wikipedia! Here's the C struct for the Windows V3 BMP: typedef struct { uint32_t header_sz; int32_t width; int32_t height; uint16_t nplanes; uint16_t bitspp; uint32_t compress_type; uint32_t bmp_bytesz; int32_t hres; int32_t vres; uint32_t ncolors; uint32_t nimpcolors; } bmp_dib_v3_header_t; --v -=-=- Afr0 Games Project Dollhouse on Github - Please fork!
Sun, 24 Oct 2010, 04:43
shroom_monk	Yup, good ol' Wikipedia was where I did the research for my program! -=-=- A mushroom a day keeps the doctor away... Keep It Simple, Shroom!