748 lines
20 KiB
C
748 lines
20 KiB
C
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/*----------------------------------------------------------------------+
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| invcmap.c - Microsoft Video 1 Compressor - Inverse Color Map. |
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| Copyright (c) 1990-1994 Microsoft Corporation. |
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| Portions Copyright Media Vision Inc. |
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| All Rights Reserved. |
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| You have a non-exclusive, worldwide, royalty-free, and perpetual |
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| license to use this source code in developing hardware, software |
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| (limited to drivers and other software required for hardware |
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| functionality), and firmware for video display and/or processing |
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| boards. Microsoft makes no warranties, express or implied, with |
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| respect to the Video 1 codec, including without limitation warranties |
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| of merchantability or fitness for a particular purpose. Microsoft |
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| shall not be liable for any damages whatsoever, including without |
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| limitation consequential damages arising from your use of the Video 1 |
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| codec. |
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+----------------------------------------------------------------------*/
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#include <math.h>
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#include <windows.h>
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#include <windowsx.h>
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#include <win32.h>
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//#pragma optimize("", off)
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int redloop(void);
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int greenloop( int restart );
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int blueloop( int restart );
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#ifdef _WIN32
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#define maxfill(pbuffer, side) \
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memset(pbuffer, -1, colormax*colormax*colormax*sizeof(LONG))
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#else
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void maxfill( DWORD _huge *buffer, long side);
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#endif
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void inv_cmap_2( int colors, BYTE colormap[3][256], int bits,
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DWORD _huge *dist_buf, LPBYTE rgbmap );
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void inv_cmap_1( int colors, BYTE colormap[3][256], int bits,
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DWORD _huge *dist_buf, LPBYTE rgbmap );
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/* Track minimum and maximum in inv_cmap_2. */
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#define MINMAX_TRACK
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BYTE NewMap[3][256];
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LPVOID FAR PASCAL MakeITable(LPRGBQUAD lprgbq, int nColors)
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{
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LPVOID lpDistBuf;
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LPBYTE lpITable;
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int i;
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lpITable = GlobalAllocPtr(GHND|GMEM_SHARE,32768l);
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if (lpITable == NULL)
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return NULL; // error no memory
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lpDistBuf = (LPVOID)GlobalAllocPtr(GHND,32768l * sizeof(DWORD));
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if (lpDistBuf == NULL) {
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GlobalFreePtr(lpITable);
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return NULL; // error no memory
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}
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for (i = 0; i < nColors; i++) {
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NewMap[0][i] = lprgbq[i].rgbRed;
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NewMap[1][i] = lprgbq[i].rgbGreen;
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NewMap[2][i] = lprgbq[i].rgbBlue;
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}
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inv_cmap_2(nColors,NewMap,5,lpDistBuf,lpITable);
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GlobalFreePtr(lpDistBuf);
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return lpITable;
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}
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static int bcenter, gcenter, rcenter;
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static long gdist, rdist, cdist;
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static long cbinc, cginc, crinc;
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static DWORD _huge *gdp;
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static DWORD _huge *rdp;
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static DWORD _huge *cdp;
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static LPBYTE grgbp;
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static LPBYTE rrgbp;
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static LPBYTE crgbp;
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static int gstride, rstride;
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static long x, xsqr, colormax;
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static int cindex;
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/*****************************************************************
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* TAG( inv_cmap_2 )
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*
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* Compute an inverse colormap efficiently.
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* Inputs:
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* colors: Number of colors in the forward colormap.
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* colormap: The forward colormap.
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* bits: Number of quantization bits. The inverse
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* colormap will have (2^bits)^3 entries.
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* dist_buf: An array of (2^bits)^3 long integers to be
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* used as scratch space.
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* Outputs:
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* rgbmap: The output inverse colormap. The entry
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* rgbmap[(r<<(2*bits)) + (g<<bits) + b]
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* is the colormap entry that is closest to the
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* (quantized) color (r,g,b).
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* Assumptions:
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* Quantization is performed by right shift (low order bits are
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* truncated). Thus, the distance to a quantized color is
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* actually measured to the color at the center of the cell
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* (i.e., to r+.5, g+.5, b+.5, if (r,g,b) is a quantized color).
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* Algorithm:
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* Uses a "distance buffer" algorithm:
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* The distance from each representative in the forward color map
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* to each point in the rgb space is computed. If it is less
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* than the distance currently stored in dist_buf, then the
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* corresponding entry in rgbmap is replaced with the current
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* representative (and the dist_buf entry is replaced with the
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* new distance).
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*
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* The distance computation uses an efficient incremental formulation.
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*
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* Distances are computed "outward" from each color. If the
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* colors are evenly distributed in color space, the expected
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* number of cells visited for color I is N^3/I.
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* Thus, the complexity of the algorithm is O(log(K) N^3),
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* where K = colors, and N = 2^bits.
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*/
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/*
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* Here's the idea: scan from the "center" of each cell "out"
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* until we hit the "edge" of the cell -- that is, the point
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* at which some other color is closer -- and stop. In 1-D,
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* this is simple:
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* for i := here to max do
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* if closer then buffer[i] = this color
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* else break
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* repeat above loop with i := here-1 to min by -1
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*
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* In 2-D, it's trickier, because along a "scan-line", the
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* region might start "after" the "center" point. A picture
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* might clarify:
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* | ...
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* | ... .
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* ... .
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* ... | .
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* . + .
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* . .
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* . .
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* .........
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*
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* The + marks the "center" of the above region. On the top 2
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* lines, the region "begins" to the right of the "center".
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*
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* Thus, we need a loop like this:
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* detect := false
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* for i := here to max do
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* if closer then
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* buffer[..., i] := this color
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* if !detect then
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* here = i
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* detect = true
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* else
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* if detect then
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* break
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*
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* Repeat the above loop with i := here-1 to min by -1. Note that
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* the "detect" value should not be reinitialized. If it was
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* "true", and center is not inside the cell, then none of the
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* cell lies to the left and this loop should exit
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* immediately.
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*
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* The outer loops are similar, except that the "closer" test
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* is replaced by a call to the "next in" loop; its "detect"
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* value serves as the test. (No assignment to the buffer is
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* done, either.)
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*
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* Each time an outer loop starts, the "here", "min", and
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* "max" values of the next inner loop should be
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* re-initialized to the center of the cell, 0, and cube size,
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* respectively. Otherwise, these values will carry over from
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* one "call" to the inner loop to the next. This tracks the
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* edges of the cell and minimizes the number of
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* "unproductive" comparisons that must be made.
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*
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* Finally, the inner-most loop can have the "if !detect"
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* optimized out of it by splitting it into two loops: one
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* that finds the first color value on the scan line that is
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* in this cell, and a second that fills the cell until
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* another one is closer:
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* if !detect then {needed for "down" loop}
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* for i := here to max do
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* if closer then
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* buffer[..., i] := this color
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* detect := true
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* break
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* for i := i+1 to max do
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* if closer then
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* buffer[..., i] := this color
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* else
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* break
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*
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* In this implementation, each level will require the
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* following variables. Variables labelled (l) are local to each
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* procedure. The ? should be replaced with r, g, or b:
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* cdist: The distance at the starting point.
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* ?center: The value of this component of the color
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* c?inc: The initial increment at the ?center position.
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* ?stride: The amount to add to the buffer
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* pointers (dp and rgbp) to get to the
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* "next row".
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* min(l): The "low edge" of the cell, init to 0
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* max(l): The "high edge" of the cell, init to
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* colormax-1
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* detect(l): True if this row has changed some
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* buffer entries.
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* i(l): The index for this row.
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* ?xx: The accumulated increment value.
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*
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* here(l): The starting index for this color. The
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* following variables are associated with here,
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* in the sense that they must be updated if here
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* is changed.
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* ?dist: The current distance for this level. The
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* value of dist from the previous level (g or r,
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* for level b or g) initializes dist on this
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* level. Thus gdist is associated with here(b)).
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* ?inc: The initial increment for the row.
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* ?dp: Pointer into the distance buffer. The value
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* from the previous level initializes this level.
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* ?rgbp: Pointer into the rgb buffer. The value
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* from the previous level initializes this level.
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*
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* The blue and green levels modify 'here-associated' variables (dp,
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* rgbp, dist) on the green and red levels, respectively, when here is
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* changed.
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*/
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void
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inv_cmap_2( int colors, BYTE colormap[3][256], int bits,
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DWORD _huge *dist_buf, LPBYTE rgbmap )
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{
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int nbits = 8 - bits;
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colormax = 1 << bits;
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x = 1 << nbits;
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xsqr = 1 << (2 * nbits);
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/* Compute "strides" for accessing the arrays. */
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gstride = (int) colormax;
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rstride = (int) (colormax * colormax);
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maxfill( dist_buf, colormax );
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for ( cindex = 0; cindex < colors; cindex++ )
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{
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/*
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* Distance formula is
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* (red - map[0])^2 + (green - map[1])^2 + (blue - map[2])^2
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*
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* Because of quantization, we will measure from the center of
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* each quantized "cube", so blue distance is
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* (blue + x/2 - map[2])^2,
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* where x = 2^(8 - bits).
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* The step size is x, so the blue increment is
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* 2*x*blue - 2*x*map[2] + 2*x^2
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*
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* Now, b in the code below is actually blue/x, so our
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* increment will be 2*(b*x^2 + x^2 - x*map[2]). For
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* efficiency, we will maintain this quantity in a separate variable
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* that will be updated incrementally by adding 2*x^2 each time.
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*/
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/* The initial position is the cell containing the colormap
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* entry. We get this by quantizing the colormap values.
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*/
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rcenter = colormap[0][cindex] >> nbits;
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gcenter = colormap[1][cindex] >> nbits;
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bcenter = colormap[2][cindex] >> nbits;
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rdist = colormap[0][cindex] - (rcenter * x + x/2);
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gdist = colormap[1][cindex] - (gcenter * x + x/2);
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cdist = colormap[2][cindex] - (bcenter * x + x/2);
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cdist = rdist*rdist + gdist*gdist + cdist*cdist;
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crinc = 2 * ((rcenter + 1) * xsqr - (colormap[0][cindex] * x));
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cginc = 2 * ((gcenter + 1) * xsqr - (colormap[1][cindex] * x));
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cbinc = 2 * ((bcenter + 1) * xsqr - (colormap[2][cindex] * x));
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/* Array starting points. */
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cdp = dist_buf + rcenter * rstride + gcenter * gstride + bcenter;
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crgbp = rgbmap + rcenter * rstride + gcenter * gstride + bcenter;
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(void)redloop();
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}
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}
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/* redloop -- loop up and down from red center. */
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int
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redloop()
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{
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int detect;
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int r, i = cindex;
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int first;
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long txsqr = xsqr + xsqr;
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static long rxx;
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detect = 0;
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/* Basic loop up. */
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for ( r = rcenter, rdist = cdist, rxx = crinc,
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rdp = cdp, rrgbp = crgbp, first = 1;
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r < (int) colormax;
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r++, rdp += rstride, rrgbp += rstride,
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rdist += rxx, rxx += txsqr, first = 0 )
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{
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if ( greenloop( first ) )
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detect = 1;
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else if ( detect )
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break;
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}
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/* Basic loop down. */
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for ( r = rcenter - 1, rxx = crinc - txsqr, rdist = cdist - rxx,
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rdp = cdp - rstride, rrgbp = crgbp - rstride, first = 1;
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r >= 0;
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r--, rdp -= rstride, rrgbp -= rstride,
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rxx -= txsqr, rdist -= rxx, first = 0 )
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{
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if ( greenloop( first ) )
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detect = 1;
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else if ( detect )
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break;
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}
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return detect;
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}
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/* greenloop -- loop up and down from green center. */
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int
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greenloop( int restart )
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{
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|||
|
|
int detect;
|
|||
|
|
int g, i = cindex;
|
|||
|
|
int first;
|
|||
|
|
long txsqr = xsqr + xsqr;
|
|||
|
|
static int here, min, max;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
static int prevmax, prevmin;
|
|||
|
|
int thismax, thismin;
|
|||
|
|
#endif
|
|||
|
|
static long ginc, gxx, gcdist; /* "gc" variables maintain correct */
|
|||
|
|
static DWORD _huge *gcdp; /* values for bcenter position, */
|
|||
|
|
static LPBYTE gcrgbp; /* despite modifications by blueloop */
|
|||
|
|
/* to gdist, gdp, grgbp. */
|
|||
|
|
|
|||
|
|
if ( restart )
|
|||
|
|
{
|
|||
|
|
here = gcenter;
|
|||
|
|
min = 0;
|
|||
|
|
max = (int) colormax - 1;
|
|||
|
|
ginc = cginc;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
prevmax = 0;
|
|||
|
|
prevmin = (int) colormax;
|
|||
|
|
#endif
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = min;
|
|||
|
|
thismax = max;
|
|||
|
|
#endif
|
|||
|
|
detect = 0;
|
|||
|
|
|
|||
|
|
/* Basic loop up. */
|
|||
|
|
for ( g = here, gcdist = gdist = rdist, gxx = ginc,
|
|||
|
|
gcdp = gdp = rdp, gcrgbp = grgbp = rrgbp, first = 1;
|
|||
|
|
g <= max;
|
|||
|
|
g++, gdp += gstride, gcdp += gstride, grgbp += gstride, gcrgbp += gstride,
|
|||
|
|
gdist += gxx, gcdist += gxx, gxx += txsqr, first = 0 )
|
|||
|
|
{
|
|||
|
|
if ( blueloop( first ) )
|
|||
|
|
{
|
|||
|
|
if ( !detect )
|
|||
|
|
{
|
|||
|
|
/* Remember here and associated data! */
|
|||
|
|
if ( g > here )
|
|||
|
|
{
|
|||
|
|
here = g;
|
|||
|
|
rdp = gcdp;
|
|||
|
|
rrgbp = gcrgbp;
|
|||
|
|
rdist = gcdist;
|
|||
|
|
ginc = gxx;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = here;
|
|||
|
|
#endif
|
|||
|
|
}
|
|||
|
|
detect = 1;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
else if ( detect )
|
|||
|
|
{
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismax = g - 1;
|
|||
|
|
#endif
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/* Basic loop down. */
|
|||
|
|
for ( g = here - 1, gxx = ginc - txsqr, gcdist = gdist = rdist - gxx,
|
|||
|
|
gcdp = gdp = rdp - gstride, gcrgbp = grgbp = rrgbp - gstride,
|
|||
|
|
first = 1;
|
|||
|
|
g >= min;
|
|||
|
|
g--, gdp -= gstride, gcdp -= gstride, grgbp -= gstride, gcrgbp -= gstride,
|
|||
|
|
gxx -= txsqr, gdist -= gxx, gcdist -= gxx, first = 0 )
|
|||
|
|
{
|
|||
|
|
if ( blueloop( first ) )
|
|||
|
|
{
|
|||
|
|
if ( !detect )
|
|||
|
|
{
|
|||
|
|
/* Remember here! */
|
|||
|
|
here = g;
|
|||
|
|
rdp = gcdp;
|
|||
|
|
rrgbp = gcrgbp;
|
|||
|
|
rdist = gcdist;
|
|||
|
|
ginc = gxx;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismax = here;
|
|||
|
|
#endif
|
|||
|
|
detect = 1;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
else if ( detect )
|
|||
|
|
{
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = g + 1;
|
|||
|
|
#endif
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
/* If we saw something, update the edge trackers. For now, only
|
|||
|
|
* tracks edges that are "shrinking" (min increasing, max
|
|||
|
|
* decreasing.
|
|||
|
|
*/
|
|||
|
|
if ( detect )
|
|||
|
|
{
|
|||
|
|
if ( thismax < prevmax )
|
|||
|
|
max = thismax;
|
|||
|
|
|
|||
|
|
prevmax = thismax;
|
|||
|
|
|
|||
|
|
if ( thismin > prevmin )
|
|||
|
|
min = thismin;
|
|||
|
|
|
|||
|
|
prevmin = thismin;
|
|||
|
|
}
|
|||
|
|
#endif
|
|||
|
|
|
|||
|
|
return detect;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/* blueloop -- loop up and down from blue center. */
|
|||
|
|
int
|
|||
|
|
blueloop( int restart )
|
|||
|
|
{
|
|||
|
|
int detect;
|
|||
|
|
register DWORD _huge *dp;
|
|||
|
|
register LPBYTE rgbp;
|
|||
|
|
register long bdist, bxx;
|
|||
|
|
register int b, i = cindex;
|
|||
|
|
register long txsqr = xsqr + xsqr;
|
|||
|
|
register int lim;
|
|||
|
|
static int here, min, max;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
static int prevmin, prevmax;
|
|||
|
|
int thismin, thismax;
|
|||
|
|
#endif /* MINMAX_TRACK */
|
|||
|
|
static long binc;
|
|||
|
|
|
|||
|
|
if ( restart )
|
|||
|
|
{
|
|||
|
|
here = bcenter;
|
|||
|
|
min = 0;
|
|||
|
|
max = (int) colormax - 1;
|
|||
|
|
binc = cbinc;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
prevmin = (int) colormax;
|
|||
|
|
prevmax = 0;
|
|||
|
|
#endif /* MINMAX_TRACK */
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
detect = 0;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = min;
|
|||
|
|
thismax = max;
|
|||
|
|
#endif
|
|||
|
|
|
|||
|
|
/* Basic loop up. */
|
|||
|
|
/* First loop just finds first applicable cell. */
|
|||
|
|
for ( b = here, bdist = gdist, bxx = binc, dp = gdp, rgbp = grgbp, lim = max;
|
|||
|
|
b <= lim;
|
|||
|
|
b++, dp++, rgbp++,
|
|||
|
|
bdist += bxx, bxx += txsqr )
|
|||
|
|
{
|
|||
|
|
if ( *dp > (DWORD)bdist )
|
|||
|
|
{
|
|||
|
|
/* Remember new 'here' and associated data! */
|
|||
|
|
if ( b > here )
|
|||
|
|
{
|
|||
|
|
here = b;
|
|||
|
|
gdp = dp;
|
|||
|
|
grgbp = rgbp;
|
|||
|
|
gdist = bdist;
|
|||
|
|
binc = bxx;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = here;
|
|||
|
|
#endif
|
|||
|
|
}
|
|||
|
|
detect = 1;
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
/* Second loop fills in a run of closer cells. */
|
|||
|
|
for ( ;
|
|||
|
|
b <= lim;
|
|||
|
|
b++, dp++, rgbp++,
|
|||
|
|
bdist += bxx, bxx += txsqr )
|
|||
|
|
{
|
|||
|
|
if ( *dp > (DWORD)bdist )
|
|||
|
|
{
|
|||
|
|
*dp = bdist;
|
|||
|
|
*rgbp = (BYTE) i;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismax = b - 1;
|
|||
|
|
#endif
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/* Basic loop down. */
|
|||
|
|
/* Do initializations here, since the 'find' loop might not get
|
|||
|
|
* executed.
|
|||
|
|
*/
|
|||
|
|
lim = min;
|
|||
|
|
b = here - 1;
|
|||
|
|
bxx = binc - txsqr;
|
|||
|
|
bdist = gdist - bxx;
|
|||
|
|
dp = gdp - 1;
|
|||
|
|
rgbp = grgbp - 1;
|
|||
|
|
/* The 'find' loop is executed only if we didn't already find
|
|||
|
|
* something.
|
|||
|
|
*/
|
|||
|
|
if ( !detect )
|
|||
|
|
for ( ;
|
|||
|
|
b >= lim;
|
|||
|
|
b--, dp--, rgbp--,
|
|||
|
|
bxx -= txsqr, bdist -= bxx )
|
|||
|
|
{
|
|||
|
|
if ( *dp > (DWORD)bdist )
|
|||
|
|
{
|
|||
|
|
/* Remember here! */
|
|||
|
|
/* No test for b against here necessary because b <
|
|||
|
|
* here by definition.
|
|||
|
|
*/
|
|||
|
|
here = b;
|
|||
|
|
gdp = dp;
|
|||
|
|
grgbp = rgbp;
|
|||
|
|
gdist = bdist;
|
|||
|
|
binc = bxx;
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismax = here;
|
|||
|
|
#endif
|
|||
|
|
detect = 1;
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
/* The 'update' loop. */
|
|||
|
|
for ( ;
|
|||
|
|
b >= lim;
|
|||
|
|
b--, dp--, rgbp--,
|
|||
|
|
bxx -= txsqr, bdist -= bxx )
|
|||
|
|
{
|
|||
|
|
if ( *dp > (DWORD)bdist )
|
|||
|
|
{
|
|||
|
|
*dp = bdist;
|
|||
|
|
*rgbp = (BYTE) i;
|
|||
|
|
}
|
|||
|
|
else
|
|||
|
|
{
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
thismin = b + 1;
|
|||
|
|
#endif
|
|||
|
|
break;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
|
|||
|
|
/* If we saw something, update the edge trackers. */
|
|||
|
|
#ifdef MINMAX_TRACK
|
|||
|
|
if ( detect )
|
|||
|
|
{
|
|||
|
|
/* Only tracks edges that are "shrinking" (min increasing, max
|
|||
|
|
* decreasing.
|
|||
|
|
*/
|
|||
|
|
if ( thismax < prevmax )
|
|||
|
|
max = thismax;
|
|||
|
|
|
|||
|
|
if ( thismin > prevmin )
|
|||
|
|
min = thismin;
|
|||
|
|
|
|||
|
|
/* Remember the min and max values. */
|
|||
|
|
prevmax = thismax;
|
|||
|
|
prevmin = thismin;
|
|||
|
|
}
|
|||
|
|
#endif /* MINMAX_TRACK */
|
|||
|
|
|
|||
|
|
return detect;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
#ifndef _WIN32
|
|||
|
|
void maxfill( DWORD _huge *buffer, long side)
|
|||
|
|
{
|
|||
|
|
register unsigned long maxv = ~0uL;
|
|||
|
|
register long i;
|
|||
|
|
register DWORD _huge *bp;
|
|||
|
|
|
|||
|
|
for ( i = colormax * colormax * colormax, bp = buffer;
|
|||
|
|
i > 0;
|
|||
|
|
i--, bp++ )
|
|||
|
|
*bp = maxv;
|
|||
|
|
}
|
|||
|
|
#endif
|
|||
|
|
|
|||
|
|
|
|||
|
|
#ifdef CMAP1
|
|||
|
|
|
|||
|
|
|
|||
|
|
/*****************************************************************
|
|||
|
|
* TAG( inv_cmap_1 )
|
|||
|
|
*
|
|||
|
|
* Compute an inverse colormap efficiently.
|
|||
|
|
* Inputs:
|
|||
|
|
|
|||
|
|
* colors: Number of colors in the forward colormap.
|
|||
|
|
* colormap: The forward colormap.
|
|||
|
|
* bits: Number of quantization bits. The inverse
|
|||
|
|
* colormap will have (2^bits)^3 entries.
|
|||
|
|
* dist_buf: An array of (2^bits)^3 long integers to be
|
|||
|
|
* used as scratch space.
|
|||
|
|
* Outputs:
|
|||
|
|
* rgbmap: The output inverse colormap. The entry
|
|||
|
|
* rgbmap[(r<<(2*bits)) + (g<<bits) + b]
|
|||
|
|
* is the colormap entry that is closest to the
|
|||
|
|
* (quantized) color (r,g,b).
|
|||
|
|
* Assumptions:
|
|||
|
|
* Quantization is performed by right shift (low order bits are
|
|||
|
|
* truncated). Thus, the distance to a quantized color is
|
|||
|
|
* actually measured to the color at the center of the cell
|
|||
|
|
* (i.e., to r+.5, g+.5, b+.5, if (r,g,b) is a quantized color).
|
|||
|
|
* Algorithm:
|
|||
|
|
* Uses a "distance buffer" algorithm:
|
|||
|
|
* The distance from each representative in the forward color map
|
|||
|
|
* to each point in the rgb space is computed. If it is less
|
|||
|
|
* than the distance currently stored in dist_buf, then the
|
|||
|
|
* corresponding entry in rgbmap is replaced with the current
|
|||
|
|
* representative (and the dist_buf entry is replaced with the
|
|||
|
|
* new distance).
|
|||
|
|
*
|
|||
|
|
* The distance computation uses an efficient incremental formulation.
|
|||
|
|
*
|
|||
|
|
* Right now, distances are computed for all entries in the rgb
|
|||
|
|
* space. Thus, the complexity of the algorithm is O(K N^3),
|
|||
|
|
* where K = colors, and N = 2^bits.
|
|||
|
|
*/
|
|||
|
|
void
|
|||
|
|
inv_cmap_1( int colors, BYTE colormap[3][256], int bits,
|
|||
|
|
DWORD _huge *dist_buf, LPBYTE rgbmap )
|
|||
|
|
{
|
|||
|
|
register DWORD _huge *dp;
|
|||
|
|
register LPBYTE rgbp;
|
|||
|
|
register long bdist, bxx;
|
|||
|
|
register int b, i;
|
|||
|
|
int nbits = 8 - bits;
|
|||
|
|
register int colormax = 1 << bits;
|
|||
|
|
register long xsqr = 1 << (2 * nbits);
|
|||
|
|
int x = 1 << nbits;
|
|||
|
|
int rinc, ginc, binc, r, g;
|
|||
|
|
long rdist, gdist, rxx, gxx;
|
|||
|
|
|
|||
|
|
for ( i = 0; i < colors; i++ )
|
|||
|
|
{
|
|||
|
|
/*
|
|||
|
|
* Distance formula is
|
|||
|
|
* (red - map[0])^2 + (green - map[1])^2 + (blue - map[2])^2
|
|||
|
|
*
|
|||
|
|
* Because of quantization, we will measure from the center of
|
|||
|
|
* each quantized "cube", so blue distance is
|
|||
|
|
* (blue + x/2 - map[2])^2,
|
|||
|
|
* where x = 2^(8 - bits).
|
|||
|
|
* The step size is x, so the blue increment is
|
|||
|
|
* 2*x*blue - 2*x*map[2] + 2*x^2
|
|||
|
|
*
|
|||
|
|
* Now, b in the code below is actually blue/x, so our
|
|||
|
|
* increment will be 2*x*x*b + (2*x^2 - 2*x*map[2]). For
|
|||
|
|
* efficiency, we will maintain this quantity in a separate variable
|
|||
|
|
* that will be updated incrementally by adding 2*x^2 each time.
|
|||
|
|
*/
|
|||
|
|
rdist = colormap[0][i] - x/2;
|
|||
|
|
gdist = colormap[1][i] - x/2;
|
|||
|
|
bdist = colormap[2][i] - x/2;
|
|||
|
|
rdist = rdist*rdist + gdist*gdist + bdist*bdist;
|
|||
|
|
|
|||
|
|
rinc = 2 * (xsqr - (colormap[0][i] << nbits));
|
|||
|
|
ginc = 2 * (xsqr - (colormap[1][i] << nbits));
|
|||
|
|
binc = 2 * (xsqr - (colormap[2][i] << nbits));
|
|||
|
|
dp = dist_buf;
|
|||
|
|
rgbp = rgbmap;
|
|||
|
|
for ( r = 0, rxx = rinc;
|
|||
|
|
r < colormax;
|
|||
|
|
rdist += rxx, r++, rxx += xsqr + xsqr )
|
|||
|
|
for ( g = 0, gdist = rdist, gxx = ginc;
|
|||
|
|
g < colormax;
|
|||
|
|
gdist += gxx, g++, gxx += xsqr + xsqr )
|
|||
|
|
for ( b = 0, bdist = gdist, bxx = binc;
|
|||
|
|
b < colormax;
|
|||
|
|
bdist += bxx, b++, dp++, rgbp++,
|
|||
|
|
bxx += xsqr + xsqr )
|
|||
|
|
{
|
|||
|
|
if ( i == 0 || *dp > bdist )
|
|||
|
|
{
|
|||
|
|
*dp = bdist;
|
|||
|
|
*rgbp = i;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
#endif
|
|||
|
|
|