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/*
libdmtx - Data Matrix Encoding/Decoding Library
Copyright (C) 2008, 2009 Mike Laughton
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Contact: mike@dragonflylogic.com
*/
/* $Id: dmtxscangrid.c 726 2009-02-19 22:17:48Z mblaughton $ */
/**
* @file dmtxscangrid.c
* @brief Scan grid tracking
*/
/**
* @brief Initialize scan grid pattern
* @param dec
* @return Initialized grid
*/
static DmtxScanGrid
InitScanGrid(DmtxDecode *dec)
{
int scale, smallestFeature;
int xExtent, yExtent, maxExtent;
int extent;
DmtxScanGrid grid;
memset(&grid, 0x00, sizeof(DmtxScanGrid));
scale = dmtxDecodeGetProp(dec, DmtxPropScale);
smallestFeature = dmtxDecodeGetProp(dec, DmtxPropScanGap) / scale;
grid.xMin = dmtxDecodeGetProp(dec, DmtxPropXmin);
grid.xMax = dmtxDecodeGetProp(dec, DmtxPropXmax);
grid.yMin = dmtxDecodeGetProp(dec, DmtxPropYmin);
grid.yMax = dmtxDecodeGetProp(dec, DmtxPropYmax);
/* Values that get set once */
xExtent = grid.xMax - grid.xMin;
yExtent = grid.yMax - grid.yMin;
maxExtent = (xExtent > yExtent) ? xExtent : yExtent;
assert(maxExtent > 1);
for(extent = 1; extent < maxExtent; extent = ((extent + 1) * 2) - 1)
if(extent <= smallestFeature)
grid.minExtent = extent;
grid.maxExtent = extent;
grid.xOffset = (grid.xMin + grid.xMax - grid.maxExtent) / 2;
grid.yOffset = (grid.yMin + grid.yMax - grid.maxExtent) / 2;
/* Values that get reset for every level */
grid.total = 1;
grid.extent = grid.maxExtent;
SetDerivedFields(&grid);
return grid;
}
/**
* @brief Return the next good location (which may be the current location),
* and advance grid progress one position beyond that. If no good
* locations remain then return DmtxRangeEnd.
* @param grid
* @return void
*/
static int
PopGridLocation(DmtxScanGrid *grid, DmtxPixelLoc *locPtr)
{
int locStatus;
do {
locStatus = GetGridCoordinates(grid, locPtr);
/* Always leave grid pointing at next available location */
grid->pixelCount++;
} while(locStatus == DmtxRangeBad);
return locStatus;
}
/**
* @brief Extract current grid position in pixel coordinates and return
* whether location is good, bad, or end
* @param grid
* @return Pixel location
*/
static int
GetGridCoordinates(DmtxScanGrid *grid, DmtxPixelLoc *locPtr)
{
int count, half, quarter;
DmtxPixelLoc loc;
/* Initially pixelCount may fall beyond acceptable limits. Update grid
* state before testing coordinates */
/* Jump to next cross pattern horizontally if current column is done */
if(grid->pixelCount >= grid->pixelTotal) {
grid->pixelCount = 0;
grid->xCenter += grid->jumpSize;
}
/* Jump to next cross pattern vertically if current row is done */
if(grid->xCenter > grid->maxExtent) {
grid->xCenter = grid->startPos;
grid->yCenter += grid->jumpSize;
}
/* Increment level when vertical step goes too far */
if(grid->yCenter > grid->maxExtent) {
grid->total *= 4;
grid->extent /= 2;
SetDerivedFields(grid);
}
if(grid->extent == 0 || grid->extent < grid->minExtent) {
locPtr->X = locPtr->Y = -1;
return DmtxRangeEnd;
}
count = grid->pixelCount;
assert(count < grid->pixelTotal);
if(count == grid->pixelTotal - 1) {
/* center pixel */
loc.X = grid->xCenter;
loc.Y = grid->yCenter;
}
else {
half = grid->pixelTotal / 2;
quarter = half / 2;
/* horizontal portion */
if(count < half) {
loc.X = grid->xCenter + ((count < quarter) ? (count - quarter) : (half - count));
loc.Y = grid->yCenter;
}
/* vertical portion */
else {
count -= half;
loc.X = grid->xCenter;
loc.Y = grid->yCenter + ((count < quarter) ? (count - quarter) : (half - count));
}
}
loc.X += grid->xOffset;
loc.Y += grid->yOffset;
*locPtr = loc;
if(loc.X < grid->xMin || loc.X > grid->xMax ||
loc.Y < grid->yMin || loc.Y > grid->yMax)
return DmtxRangeBad;
return DmtxRangeGood;
}
/**
* @brief Update derived fields based on current state
* @param grid
* @return void
*/
static void
SetDerivedFields(DmtxScanGrid *grid)
{
grid->jumpSize = grid->extent + 1;
grid->pixelTotal = 2 * grid->extent - 1;
grid->startPos = grid->extent / 2;
grid->pixelCount = 0;
grid->xCenter = grid->yCenter = grid->startPos;
}
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