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Fixed combineCloseBoxes logic issues that affected accuracy

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This commit is contained in:
Matt Hill
2015-09-23 22:47:56 -04:00
parent 09b7178322
commit c93667ed74
2 changed files with 54 additions and 8 deletions
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60
src/openalpr/segmentation/charactersegmenter.cpp
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@@ -159,7 +159,7 @@ namespace alpr
getTimeMonotonic(&startTime);
filterEdgeBoxes(pipeline_data->thresholds, candidateBoxes, medianCharWidth, avgCharHeight);
candidateBoxes = combineCloseBoxes(candidateBoxes, medianCharWidth);
candidateBoxes = combineCloseBoxes(candidateBoxes);
candidateBoxes = filterMostlyEmptyBoxes(pipeline_data->thresholds, candidateBoxes);
@@ -409,8 +409,40 @@ namespace alpr
}
}
vector<Rect> CharacterSegmenter::combineCloseBoxes( vector<Rect> charBoxes, float biggestCharWidth)
vector<Rect> CharacterSegmenter::combineCloseBoxes( vector<Rect> charBoxes)
{
// Don't bother combining if there are 2 or fewer characters
if (charBoxes.size() <= 2)
return charBoxes;
// First find the median char gap (the space between characters)
vector<int> char_gaps;
for (unsigned int i = 0; i < charBoxes.size(); i++)
{
if (i == charBoxes.size() - 1)
break;
// the space between charbox i and i+1
int char_gap = charBoxes[i+1].x - (charBoxes[i].x + charBoxes[i].width);
char_gaps.push_back(char_gap);
}
int median_char_gap = median(char_gaps.data(), char_gaps.size());
// Find the second largest char box. Should help ignore a big outlier
vector<int> char_sizes;
float biggestCharWidth;
for (unsigned int i = 0; i < charBoxes.size(); i++)
{
char_sizes.push_back(charBoxes[i].width);
}
std::sort(char_sizes.begin(), char_sizes.end());
biggestCharWidth = char_sizes[char_sizes.size() - 2];
vector<Rect> newCharBoxes;
for (unsigned int i = 0; i < charBoxes.size(); i++)
@@ -422,12 +454,26 @@ namespace alpr
}
float bigWidth = (charBoxes[i + 1].x + charBoxes[i + 1].width - charBoxes[i].x);
float w1Diff = abs(charBoxes[i].width - biggestCharWidth);
float w2Diff = abs(charBoxes[i + 1].width - biggestCharWidth);
float bigDiff = abs(bigWidth - biggestCharWidth);
bigDiff *= 1.3; // Make it a little harder to merge boxes.
float left_gap;
float right_gap;
if (i == 0)
left_gap = 999999999999;
else
left_gap = charBoxes[i].x - (charBoxes[i-1].x + charBoxes[i-1].width);
right_gap = charBoxes[i+1].x - (charBoxes[i].x + charBoxes[i].width);
int min_gap = (int) ((float)median_char_gap) * 0.75;
int max_gap = (int) ((float)median_char_gap) * 1.25;
int max_width = (int) ((float)biggestCharWidth) * 1.1;
bool has_good_gap = (left_gap >= min_gap && left_gap <= max_gap) || (right_gap >= min_gap && right_gap <= max_gap);
if (bigDiff < w1Diff && bigDiff < w2Diff)
if (has_good_gap && bigWidth <= max_width)
{
Rect bigRect(charBoxes[i].x, charBoxes[i].y, bigWidth, charBoxes[i].height);
newCharBoxes.push_back(bigRect);

2
src/openalpr/segmentation/charactersegmenter.h
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@@ -68,7 +68,7 @@ namespace alpr
std::vector<cv::Rect> getHistogramBoxes(HistogramVertical histogram, float avgCharWidth, float avgCharHeight, float* score);
std::vector<cv::Rect> getBestCharBoxes(cv::Mat img, std::vector<cv::Rect> charBoxes, float avgCharWidth);
std::vector<cv::Rect> combineCloseBoxes( std::vector<cv::Rect> charBoxes, float avgCharWidth);
std::vector<cv::Rect> combineCloseBoxes( std::vector<cv::Rect> charBoxes);
std::vector<cv::Rect> get1DHits(cv::Mat img, int yOffset);