; $Id: read_bmp.pro,v 1.17 2004/01/21 15:54:59 scottm Exp $ ; ; Copyright (c) 1993-2004, Research Systems, Inc. All rights reserved. ; Unauthorized reproduction prohibited. FUNCTION READ_BMP, File, Red, Green, Blue, Ihdr, RGB=rgb ;+ ; NAME: ; READ_BMP ; ; PURPOSE: ; This function reads a Microsoft Windows Version 3 device ; independent bitmap file (.BMP). ; ; CATEGORY: ; Input/Output ; ; CALLING SEQUENCE: ; Result = READ_BMP(File [, R, G, B [, IHDR]]) ; ; INPUTS: ; File: The full path name of the bitmap file to read. ; ; OUTPUTS: ; This function returns a byte array containing the image ; from the bitmap file. In the case of 4-bit or 8-bit images, ; the dimensions of the resulting array are [biWidth, biHeight]; ; for 16 and 24-bit decomposed color images the dimensions are ; [3, biWidth, biHeight]. ; Dimensions are taken from the BITMAPINFOHEADER of the file. ; NOTE: for 24 bit images, unless the RGB keyword is supplied, ; color interleaving is blue, green, red; ; i.e. result[0,i,j] = blue, result[1,i,j] = green, etc. ; ; OPTIONAL OUTPUTS: ; R, G, B: Color tables from the file. There 16 elements each for ; 4 bit images, 256 elements each for 8 bit images. Not ; defined or used for 16 and 24 bit images. ; Ihdr: A structure containing BITMAPINFOHEADER from file. ; Tag names are as defined in the MS Windows Programmer's ; Reference Manual, Chapter 7. ; ; KEYWORDDS: ; RGB: If this keyword is supplied, and a 16 or 24-bit image is read, ; color interleaving of the result is R, G, B, rather than BGR. ; Result[0,i,j] = red, Result[1,i,j] = green, and ; Result[2,i,j] = blue. ; SIDE EFFECTS: ; IO is performed. ; ; RESTRICTIONS: ; DOES NOT HANDLE: 1 bit deep images, or compressed images. ; Is not fast for 4 bit images. Works best on images where the ; number of bytes in each scan-line is evenly divisible by 4. ; ; PROCEDURE: ; Straightforward. Will work on both big endian and little endian ; machines. ; ; EXAMPLE: ; TV, READ_BMP('c:\windows\party.bmp', r, g, b) ;Read & display image ; TVLCT, r, g, b ;Load it's colors ; ; MODIFICATION HISTORY: ; DMS, RSI. March 1993. Original version. ; DMS, RSI. May, 1993. Now works on all machines... ; DMS, RSI. Nov, 1996 Added support for 16-bit RGB and RGB keyword. ; CT, RSI, Aug 2003: Fix bug in error code if unable to open file. ;- on_ioerror, bad on_error, 2 ;Return on error openr, unit, file, /GET_LUN, /BLOCK fhdr = { BITMAPFILEHEADER, $ bftype: bytarr(2), $ ;A two char string bfsize: 0L, $ bfreserved1: 0, $ bfreserved2: 0, $ bfoffbits: 0L $ } readu, unit, fhdr ;Read the bitmapfileheader if string(fhdr.bftype) ne "BM" then begin free_lun,unit message, 'File '+file+' is not in bitmap file format' endif ihdr = { BITMAPINFOHEADER, $ bisize: 0L, $ biwidth: 0L, $ biheight: 0L, $ biplanes: 0, $ bibitcount: 0, $ bicompression: 0L, $ bisizeimage: 0L, $ bixpelspermeter: 0L, $ biypelspermeter: 0L, $ biclrused: 0L, $ biclrimportant: 0L $ } readu, unit, ihdr big_endian = (byte(1,0,2))[0] eq 0b if big_endian then begin ;Big endian machine? fhdr = swap_endian(fhdr) ;Yes, swap it ihdr = swap_endian(ihdr) endif if ihdr.bibitcount eq 1 then begin free_lun, unit message, 'Can''t handle monochrome images' endif if ihdr.bicompression ne 0 then begin free_lun, unit message, 'Can''t handle compressed images' endif ;Pseudo color? if (ihdr.bibitcount ne 24) and (ihdr.bibitcount ne 16) then begin colors = bytarr(4, 2^ihdr.bibitcount) readu, unit, colors ;Read colors red = reform(colors[2, *]) ;Decommutate colors green = reform(colors[1, *]) blue = reform(colors[0, *]) endif nx = ihdr.biwidth ;Columns ny = ihdr.biheight ;Rows point_lun, unit, fhdr.bfoffbits ;Point to data... case ihdr.bibitcount of ;How many bits/pixel? 4: begin a = bytarr(nx, ny, /nozero) buff = bytarr(nx/2, /nozero) ;Line buffer even = lindgen(nx/2) * 2 odd = even + 1 if nx and 1 then pad = 0B ;interbyte padding i = (n_elements(buff) + n_elements(pad)) and 3 ;bytes we have if i ne 0 then pad = bytarr(4-i+n_elements(pad)) for i=0, ny-1 do begin if n_elements(pad) ne 0 then readu, unit, buff, pad $ else readu, unit, buff a[even, i] = ishft(buff, -4) a[odd, i] = buff and 15b if nx and 1 then a[nx-1, i] = ishft(pad[0], -4) ;Last odd byte? endfor endcase 8: begin a = bytarr(nx, ny, /nozero) if (nx and 3) eq 0 then readu, unit, a $ ;Slam dunk it else begin ;Must read line by line... pad = bytarr(4 - (nx and 3)) buff = bytarr(nx, /nozero) for i=0, ny-1 do begin ;Each line readu, unit, buff, pad a[0,i] = buff endfor endelse endcase ;8 bits/pixel 16: begin ;16 bits/pixel ; bits(0:4) = blue ; bits(5:9) = green ; bits(10:14) = red a = intarr(nx * ny, /nozero) ;Read as a 1D array if (nx and 1) eq 0 then readu, unit, a $ ;If even # of cols, no padding else begin pad = 0 ;Pad 1 16 bit word buff = intarr(nx, /nozero) for i=0, ny-1 do begin readu, unit, buff, pad a[i * nx] = buff ;Insert line endfor endelse if big_endian then byteorder, a, /sswap r = byte(ishft(a,-7) and 248) ;Shift down 10 and up 3 g = byte(ishft(a,-2) and 248) ;down 5 and up 3 a = byte(ishft(a, 3) and 248) ;up 3, really blue if keyword_set(RGB) then a = [r,g,a] $ ;Unswitch it? else a = [a,g,r] a = reform(a, nx * ny, 3, /overwrite) ;Diddle to 3,nx,ny a = transpose(temporary(a)) ;Color interleave in 1st dimension a = reform(a,3,nx,ny,/overwrite) endcase ;16 bits 24: begin ;24 bits / pixel.... a = bytarr(3, nx, ny, /nozero) if ((3 * nx) and 3) eq 0 then readu, unit, a $ ;Again, dunk it. else begin pad = bytarr(4 - ((3 * nx) and 3)) buff = bytarr(3, nx, /nozero) for i=0, ny-1 do begin readu, unit, buff, pad a[0,0, i] = buff ;Insert line endfor endelse if keyword_set(RGB) then begin ;Unswitch it? buff = a[0,*,*] a[0,0,0] = a[2,*,*] a[2,0,0] = buff endif endcase ;24bits else: begin free_lun,unit Message,'Can not handle '+strtrim(ihdr.bibitcount,2)+' bits/pixel' endcase endcase free_lun, unit return, a bad: if n_elements(unit) gt 0 then $ if (unit ne 0) then free_lun, unit Message, 'Can''t open (or read)' + file return, 0 end