+/** A linear threshold determination function.
+*/
+
+static inline int32_t linearstep( int32_t edge1, int32_t edge2, int32_t a )
+{
+ if ( a < edge1 )
+ return 0;
+
+ if ( a >= edge2 )
+ return 0x10000;
+
+ return ( ( a - edge1 ) << 16 ) / ( edge2 - edge1 );
+}
+
+/** A smoother, non-linear threshold determination function.
+*/
+
+static inline int32_t smoothstep( int32_t edge1, int32_t edge2, uint32_t a )
+{
+ if ( a < edge1 )
+ return 0;
+
+ if ( a >= edge2 )
+ return 0x10000;
+
+ a = ( ( a - edge1 ) << 16 ) / ( edge2 - edge1 );
+
+ return ( ( ( a * a ) >> 16 ) * ( ( 3 << 16 ) - ( 2 * a ) ) ) >> 16;
+}
+
+/** Load the luma map from PGM stream.
+*/
+
+static void luma_read_pgm( FILE *f, uint16_t **map, int *width, int *height )
+{
+ uint8_t *data = NULL;
+ while (1)
+ {
+ char line[128];
+ char comment[128];
+ int i = 2;
+ int maxval;
+ int bpp;
+ uint16_t *p;
+
+ line[127] = '\0';
+
+ // get the magic code
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ // skip comments
+ while ( sscanf( line, " #%s", comment ) > 0 )
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ if ( line[0] != 'P' || line[1] != '5' )
+ break;
+
+ // skip white space and see if a new line must be fetched
+ for ( i = 2; i < 127 && line[i] != '\0' && isspace( line[i] ); i++ );
+ if ( ( line[i] == '\0' || line[i] == '#' ) && fgets( line, 127, f ) == NULL )
+ break;
+
+ // skip comments
+ while ( sscanf( line, " #%s", comment ) > 0 )
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ // get the dimensions
+ if ( line[0] == 'P' )
+ i = sscanf( line, "P5 %d %d %d", width, height, &maxval );
+ else
+ i = sscanf( line, "%d %d %d", width, height, &maxval );
+
+ // get the height value, if not yet
+ if ( i < 2 )
+ {
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ // skip comments
+ while ( sscanf( line, " #%s", comment ) > 0 )
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ i = sscanf( line, "%d", height );
+ if ( i == 0 )
+ break;
+ else
+ i = 2;
+ }
+
+ // get the maximum gray value, if not yet
+ if ( i < 3 )
+ {
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ // skip comments
+ while ( sscanf( line, " #%s", comment ) > 0 )
+ if ( fgets( line, 127, f ) == NULL )
+ break;
+
+ i = sscanf( line, "%d", &maxval );
+ if ( i == 0 )
+ break;
+ }
+
+ // determine if this is one or two bytes per pixel
+ bpp = maxval > 255 ? 2 : 1;
+
+ // allocate temporary storage for the raw data
+ data = mlt_pool_alloc( *width * *height * bpp );
+ if ( data == NULL )
+ break;
+
+ // read the raw data
+ if ( fread( data, *width * *height * bpp, 1, f ) != 1 )
+ break;
+
+ // allocate the luma bitmap
+ *map = p = (uint16_t*)mlt_pool_alloc( *width * *height * sizeof( uint16_t ) );
+ if ( *map == NULL )
+ break;
+
+ // proces the raw data into the luma bitmap
+ for ( i = 0; i < *width * *height * bpp; i += bpp )
+ {
+ if ( bpp == 1 )
+ *p++ = data[ i ] << 8;
+ else
+ *p++ = ( data[ i ] << 8 ) + data[ i+1 ];
+ }
+
+ break;
+ }
+
+ if ( data != NULL )
+ mlt_pool_release( data );
+}
+
+/** Generate a luma map from any YUV image.
+*/
+
+static void luma_read_yuv422( uint8_t *image, uint16_t **map, int width, int height )
+{
+ int i;
+
+ // allocate the luma bitmap
+ uint16_t *p = *map = ( uint16_t* )mlt_pool_alloc( width * height * sizeof( uint16_t ) );
+ if ( *map == NULL )
+ return;
+
+ // proces the image data into the luma bitmap
+ for ( i = 0; i < width * height * 2; i += 2 )
+ *p++ = ( image[ i ] - 16 ) * 299; // 299 = 65535 / 219
+}
+