jsqrcode
Version:
a node port of Lazar Laszlo's `jsqrcode` qr code decoder
325 lines (278 loc) • 11.1 kB
JavaScript
/*
Ported to JavaScript by Lazar Laszlo 2011
lazarsoft@gmail.com, www.lazarsoft.info
*/
/*
*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
var grid = require('./grid');
var Version = require('./version');
var PerspectiveTransform = require('./perspective-transform');
var qrcode = require('./qrcode')();
var AlignmentPatternFinder = require('./alignpat');
var FinderPatternFinder = require('./findpat');
function DetectorResult(bits, points)
{
this.bits = bits;
this.points = points;
}
function Detector(image)
{
this.image=image;
this.resultPointCallback = null;
this.sizeOfBlackWhiteBlackRun=function( fromX, fromY, toX, toY)
{
// Mild variant of Bresenham's algorithm;
// see http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
var steep = Math.abs(toY - fromY) > Math.abs(toX - fromX);
if (steep)
{
var temp = fromX;
fromX = fromY;
fromY = temp;
temp = toX;
toX = toY;
toY = temp;
}
var dx = Math.abs(toX - fromX);
var dy = Math.abs(toY - fromY);
var error = - dx >> 1;
var ystep = fromY < toY?1:- 1;
var xstep = fromX < toX?1:- 1;
var state = 0; // In black pixels, looking for white, first or second time
for (var x = fromX, y = fromY; x != toX; x += xstep)
{
var realX = steep?y:x;
var realY = steep?x:y;
if (state == 1)
{
// In white pixels, looking for black
if (this.image[realX + realY*qrcode.width])
{
state++;
}
}
else
{
if (!this.image[realX + realY*qrcode.width])
{
state++;
}
}
if (state == 3)
{
// Found black, white, black, and stumbled back onto white; done
var diffX = x - fromX;
var diffY = y - fromY;
return Math.sqrt( (diffX * diffX + diffY * diffY));
}
error += dy;
if (error > 0)
{
if (y == toY)
{
break;
}
y += ystep;
error -= dx;
}
}
var diffX2 = toX - fromX;
var diffY2 = toY - fromY;
return Math.sqrt( (diffX2 * diffX2 + diffY2 * diffY2));
}
this.sizeOfBlackWhiteBlackRunBothWays=function( fromX, fromY, toX, toY)
{
var result = this.sizeOfBlackWhiteBlackRun(fromX, fromY, toX, toY);
// Now count other way -- don't run off image though of course
var scale = 1.0;
var otherToX = fromX - (toX - fromX);
if (otherToX < 0)
{
scale = fromX / (fromX - otherToX);
otherToX = 0;
}
else if (otherToX >= qrcode.width)
{
scale = (qrcode.width - 1 - fromX) / (otherToX - fromX);
otherToX = qrcode.width - 1;
}
var otherToY = Math.floor (fromY - (toY - fromY) * scale);
scale = 1.0;
if (otherToY < 0)
{
scale = fromY / (fromY - otherToY);
otherToY = 0;
}
else if (otherToY >= qrcode.height)
{
scale = (qrcode.height - 1 - fromY) / (otherToY - fromY);
otherToY = qrcode.height - 1;
}
otherToX = Math.floor (fromX + (otherToX - fromX) * scale);
result += this.sizeOfBlackWhiteBlackRun(fromX, fromY, otherToX, otherToY);
return result - 1.0; // -1 because we counted the middle pixel twice
}
this.calculateModuleSizeOneWay=function( pattern, otherPattern)
{
var moduleSizeEst1 = this.sizeOfBlackWhiteBlackRunBothWays(Math.floor( pattern.X), Math.floor( pattern.Y), Math.floor( otherPattern.X), Math.floor(otherPattern.Y));
var moduleSizeEst2 = this.sizeOfBlackWhiteBlackRunBothWays(Math.floor(otherPattern.X), Math.floor(otherPattern.Y), Math.floor( pattern.X), Math.floor(pattern.Y));
if (isNaN(moduleSizeEst1))
{
return moduleSizeEst2 / 7.0;
}
if (isNaN(moduleSizeEst2))
{
return moduleSizeEst1 / 7.0;
}
// Average them, and divide by 7 since we've counted the width of 3 black modules,
// and 1 white and 1 black module on either side. Ergo, divide sum by 14.
return (moduleSizeEst1 + moduleSizeEst2) / 14.0;
}
this.calculateModuleSize=function( topLeft, topRight, bottomLeft)
{
// Take the average
return (this.calculateModuleSizeOneWay(topLeft, topRight) + this.calculateModuleSizeOneWay(topLeft, bottomLeft)) / 2.0;
}
this.distance=function( pattern1, pattern2)
{
xDiff = pattern1.X - pattern2.X;
yDiff = pattern1.Y - pattern2.Y;
return Math.sqrt( (xDiff * xDiff + yDiff * yDiff));
}
this.computeDimension=function( topLeft, topRight, bottomLeft, moduleSize)
{
var tltrCentersDimension = Math.round(this.distance(topLeft, topRight) / moduleSize);
var tlblCentersDimension = Math.round(this.distance(topLeft, bottomLeft) / moduleSize);
var dimension = ((tltrCentersDimension + tlblCentersDimension) >> 1) + 7;
switch (dimension & 0x03)
{
// mod 4
case 0:
dimension++;
break;
// 1? do nothing
case 2:
dimension--;
break;
case 3:
throw "Error";
}
return dimension;
}
this.findAlignmentInRegion=function( overallEstModuleSize, estAlignmentX, estAlignmentY, allowanceFactor)
{
// Look for an alignment pattern (3 modules in size) around where it
// should be
var allowance = Math.floor (allowanceFactor * overallEstModuleSize);
var alignmentAreaLeftX = Math.max(0, estAlignmentX - allowance);
var alignmentAreaRightX = Math.min(qrcode.width - 1, estAlignmentX + allowance);
if (alignmentAreaRightX - alignmentAreaLeftX < overallEstModuleSize * 3)
{
throw "Error";
}
var alignmentAreaTopY = Math.max(0, estAlignmentY - allowance);
var alignmentAreaBottomY = Math.min(qrcode.height - 1, estAlignmentY + allowance);
var alignmentFinder = new AlignmentPatternFinder(this.image, alignmentAreaLeftX, alignmentAreaTopY, alignmentAreaRightX - alignmentAreaLeftX, alignmentAreaBottomY - alignmentAreaTopY, overallEstModuleSize, this.resultPointCallback);
return alignmentFinder.find();
}
this.createTransform=function( topLeft, topRight, bottomLeft, alignmentPattern, dimension)
{
var dimMinusThree = dimension - 3.5;
var bottomRightX;
var bottomRightY;
var sourceBottomRightX;
var sourceBottomRightY;
if (alignmentPattern != null)
{
bottomRightX = alignmentPattern.X;
bottomRightY = alignmentPattern.Y;
sourceBottomRightX = sourceBottomRightY = dimMinusThree - 3.0;
}
else
{
// Don't have an alignment pattern, just make up the bottom-right point
bottomRightX = (topRight.X - topLeft.X) + bottomLeft.X;
bottomRightY = (topRight.Y - topLeft.Y) + bottomLeft.Y;
sourceBottomRightX = sourceBottomRightY = dimMinusThree;
}
var transform = PerspectiveTransform.quadrilateralToQuadrilateral(3.5, 3.5, dimMinusThree, 3.5, sourceBottomRightX, sourceBottomRightY, 3.5, dimMinusThree, topLeft.X, topLeft.Y, topRight.X, topRight.Y, bottomRightX, bottomRightY, bottomLeft.X, bottomLeft.Y);
return transform;
}
this.sampleGrid = function( image, transform, dimension)
{
var sampler = grid;
return sampler.sampleGrid3(image, dimension, transform);
}
this.processFinderPatternInfo = function( info)
{
var topLeft = info.TopLeft;
var topRight = info.TopRight;
var bottomLeft = info.BottomLeft;
var moduleSize = this.calculateModuleSize(topLeft, topRight, bottomLeft);
if (moduleSize < 1.0)
{
throw "Error";
}
var dimension = this.computeDimension(topLeft, topRight, bottomLeft, moduleSize);
var provisionalVersion = Version.getProvisionalVersionForDimension(dimension);
var modulesBetweenFPCenters = provisionalVersion.DimensionForVersion - 7;
var alignmentPattern = null;
// Anything above version 1 has an alignment pattern
if (provisionalVersion.AlignmentPatternCenters.length > 0)
{
// Guess where a "bottom right" finder pattern would have been
var bottomRightX = topRight.X - topLeft.X + bottomLeft.X;
var bottomRightY = topRight.Y - topLeft.Y + bottomLeft.Y;
// Estimate that alignment pattern is closer by 3 modules
// from "bottom right" to known top left location
var correctionToTopLeft = 1.0 - 3.0 / modulesBetweenFPCenters;
var estAlignmentX = Math.floor (topLeft.X + correctionToTopLeft * (bottomRightX - topLeft.X));
var estAlignmentY = Math.floor (topLeft.Y + correctionToTopLeft * (bottomRightY - topLeft.Y));
// Kind of arbitrary -- expand search radius before giving up
for (var i = 4; i <= 16; i <<= 1)
{
//try
//{
alignmentPattern = this.findAlignmentInRegion(moduleSize, estAlignmentX, estAlignmentY, i);
break;
//}
//catch (re)
//{
// try next round
//}
}
// If we didn't find alignment pattern... well try anyway without it
}
var transform = this.createTransform(topLeft, topRight, bottomLeft, alignmentPattern, dimension);
var bits = this.sampleGrid(this.image, transform, dimension);
var points;
if (alignmentPattern == null)
{
points = new Array(bottomLeft, topLeft, topRight);
}
else
{
points = new Array(bottomLeft, topLeft, topRight, alignmentPattern);
}
return new DetectorResult(bits, points);
}
this.detect = function() {
var info = new FinderPatternFinder().findFinderPattern(this.image);
return this.processFinderPatternInfo(info);
}
}
module.exports = Detector;