more comments, made endian checking run-time

diff --git a/Applications/fview/fview.c b/Applications/fview/fview.c
index b79003c..26da5e5 100644 (file)
--- a/Applications/fview/fview.c
+++ b/Applications/fview/fview.c
@@ -79,7 +79,7 @@ int pinfo=0;                /* just print info from bmp header and quit */
 int rsize;                  /* bmp size of row in bytes */
 int ssize;                  /* screen size of row in bytes */
 
-#ifndef LITTLE_ENDIAN
+
 uint16_t swizzle16( uint16_t d ){
        return d << 8 | d >> 8 ;
 }
@@ -91,9 +91,16 @@ uint32_t swizzle32( uint32_t d ){
                ( d << 8 ) & 0xff0000  |
                ( d << 24 );
 }
-#endif
 
 
+/* Return true if big endian */
+int big_endian(){
+       uint16_t w = 0x1234;
+       uint8_t *c = (uint8_t *) w;
+       if( *c == 0x12 ) return 1;
+       return 0;
+}
+
 /* scan the tty driver's nodes.  Pick the one that gives us the most resolution at 1bpp, and can do a direct WRITE ioctl */
 int scan_modes(void) {
   int i = 0;
@@ -112,7 +119,6 @@ int scan_modes(void) {
                  break;
          if( ! (disp.commands & GFX_WRITE) ) continue;
          if( ! (disp.format & FMT_MONO_WB) ) continue;
-         //      if( disp.width != 256 ) continue;
          res = disp.width * disp.height;
          if( res > maxres ){
                  maxres = res;
@@ -156,8 +162,8 @@ void flip_err( void ){
        }
 }
 
-/* Floyd-Steinberg Dithering */
-void fs_dist( int16_t e, uint16_t i ){ 
+/* Floyd-Steinberg Dithering - distribute luminance error amongst forward neighbors */
+void fs_dist( int16_t e, uint16_t i ){
        /* distribute error */
        if( dither ){
                err_cur[ i + 1 ] = e * 7 ;
@@ -177,20 +183,25 @@ void bpp32( int no ){
        struct bmp_palette p;
 
        flip_err();
+
        memset( err_next, 0, (disp.width+2)*sizeof(int) );
+
        for( i=0; i<ssize; i++){
                c=0;
                for( j=0; j<8; j++ ){
                        if( in < lbuf + rsize ){
-                               /* fixme: the following color translation only
-                                  works with big endian... add a ifdef for little */
                                switch( no ){
                                case 16:
+                                       /* bit manip a 5-5-5-1 layout,
+                                          while scaling the result up to 
+                                          8bits from 5.
+                                       */
                                        p.green = (*(in+1) << 1) & 0xf8;
                                        p.red   = (*(in+1) << 6) | *in >> 5;
                                        p.blue  = *in << 3 ;
                                        in += 2;
                                        break;
+                                       /* 32 is just 24 with a leading 0 */
                                case 32:
                                        in++;
                                case 24:
@@ -200,6 +211,7 @@ void bpp32( int no ){
                                }
                        }
                        else{
+                               /* we're past src line end... make blank. */
                                p.green = 0;
                                p.red = 0 ;
                                p.blue = 0 ;
@@ -218,10 +230,9 @@ void bpp32( int no ){
                        fs_dist( e, erri );
                        erri++;
                }
-               *out++ = c;
+               *out++ = c; /* every 8 samples write c to dest
        }
-       
-}      
+}
 
 
 /* Convert 1 row of paletted mode to 1 bpp screen row */
@@ -341,10 +352,10 @@ int main( int argc, char *argv[] )
                exit_err_mess("Error reading bmp file header");
 
        /* swizzle bitmap fields */
-#ifndef LITTLE_ENDIAN
-       h.size = swizzle32( h.size );
-       h.offset = swizzle32( h.offset );
-#endif
+       if( big_endian() ){
+               h.size = swizzle32( h.size );
+               h.offset = swizzle32( h.offset );
+       }
 
        /* get dib header */
        ret = read( fd, &d, sizeof(d) );
@@ -352,17 +363,17 @@ int main( int argc, char *argv[] )
                exit_err_mess("Error reading dib header");
 
        /* swizzle its fields */
-#ifndef LITTLE_ENDIAN
-       d.size = swizzle32( d.size );
-       d.width = swizzle32( d.width );
-       d.height = swizzle32( d.height );
-       d.planes = swizzle16( d.planes );
-       d.bpp = swizzle16( d.bpp );
-       d.comp = swizzle32( d.comp );
-       d.dsize = swizzle32( d.dsize );
-       /* -- skip swizzling some unused data -- */
-       d.colors = swizzle32( d.colors );
-#endif
+       if( big_endian() ){
+               d.size = swizzle32( d.size );
+               d.width = swizzle32( d.width );
+               d.height = swizzle32( d.height );
+               d.planes = swizzle16( d.planes );
+               d.bpp = swizzle16( d.bpp );
+               d.comp = swizzle32( d.comp );
+               d.dsize = swizzle32( d.dsize );
+               /* -- skip swizzling some unused data -- */
+               d.colors = swizzle32( d.colors );
+       }
 
        /* get pallete table */
        if( lseek( fd, sizeof(h)+d.size, SEEK_SET ) < 0 )