4.3.8: fix #7: Histogram

src/tools/histogram-viewer/histogram_viewer.cpp

@@ -2,12 +2,6 @@
     Copyright (C) 2020 Arindam Chaudhuri <ksharindam@gmail.com>
 */
 #include "histogram_viewer.h"
-#include <cmath>
-#include <QPainter>
-#include <QGridLayout>
-#include <QHBoxLayout>
-#include <QCheckBox>
-#include <QDialogButtonBox>
 
 
 #define PLUGIN_NAME "Histogram Viewer"
@@ -18,133 +12,117 @@ Q_EXPORT_PLUGIN2(histogram-viewer, ToolPlugin);
 
 //********* ---------- Histogram Viewer --------- ********** //
 
-void getHistogram(QImage &img, uint hist_r[], uint hist_g[], uint hist_b[], uint hist_y[])
+void getHistogram(QImage &img, uint hist_r[], uint hist_g[], uint hist_b[])
 {
     int w = img.width();
     int h = img.height();
+    int x, y, r, g, b;
 
-    for (int y=0; y<h; y++) {
+    for (y = 0; y < h; y++)
+    {
         QRgb *row = (QRgb*) img.constScanLine(y);
-        for (int x=0; x<w; x++) {
-            int r = qRed(row[x]);
-            int g = qGreen(row[x]);
-            int b = qBlue(row[x]);
-            int Y = r*0.2126f + g*0.7152f + b*0.0722f;
+        for (x=0; x<w; x++)
+        {
+            r = qRed(row[x]);
+            g = qGreen(row[x]);
+            b = qBlue(row[x]);
             ++hist_r[r];
             ++hist_g[g];
             ++hist_b[b];
-            ++hist_y[Y];
         }
     }
 }
 
-template<typename T>
-QImage histogramImage(T histogram[], QColor color, int hist_w, int hist_h)
+template<typename T> QImage histogramImage(T histr[], T histg[], T histb[], int hist_w, int hist_h, bool logarithmic)
 {
     // get maximum in each histogram
-    T max_val=0;
-    for (int i=0; i<256; i++) {
-        if (histogram[i] > max_val) max_val = histogram[i];
+    T max_val = 0;
+    int i, j, i1, x, ro, go, bo;
+    float factorh, factorl, factorw;
+    float r, g, b, k, ix, kx;
+    for (i = 0; i < 256; i++)
+    {
+        if (histr[i] > max_val) max_val = histr[i];
+        if (histg[i] > max_val) max_val = histg[i];
+        if (histb[i] > max_val) max_val = histb[i];
     }
     // create histogram image and draw histogram
-    double factor = (double)hist_h / max_val;
+    factorh = (float)max_val / (float)hist_h;
+    factorl = (max_val > 0) ? (float)max_val / log((float)max_val + 1.0f) : 1.0f;
+    factorw = 256.0f / (float)hist_w;
 
-    QImage hist_img(hist_w+2, hist_h+2, QImage::Format_RGB32);
-    hist_img.fill(Qt::white);
+    QImage hist_img(hist_w, hist_h, QImage::Format_RGB32);
 
-    QPainter painter(&hist_img);
-    // draw outline and grid
-    painter.drawRect(0,0, hist_w+1, hist_h+1);
-    painter.setPen(QColor(220,220,220));
-    for (int i=1; i<5; i++) {
-        painter.drawLine(QPoint(i*255/5,1), QPoint(i*255/5,hist_h));
-    }
     // draw histogram bars
-    painter.setPen(color);
-    for (int i=0; i<256; i++) {
-        int line_height = factor*histogram[i];
-        if (line_height==0)
-            continue;
-        QPoint start(i+1, 1);
-        QPoint end(i+1, line_height);
-        painter.drawLine(start, end);
+    for (j = 0; j < hist_h; j++)
+    {
+        QRgb *row = (QRgb*)hist_img.constScanLine(j);
+        for (x = 0; x < hist_w; x++)
+        {
+            ix = factorw * x;
+            i = (int)ix;
+            i1 = ((i + 1) < hist_w) ? (i + 1) : i;
+            kx = ix - i;
+            k = (float)max_val - (float)j * factorh;
+            r = ((1.0f - kx) * (float)histr[i] + kx * (float)histr[i1]);
+            g = ((1.0f - kx) * (float)histg[i] + kx * (float)histg[i1]);
+            b = ((1.0f - kx) * (float)histb[i] + kx * (float)histb[i1]);
+            if (logarithmic)
+            {
+                r = log(r + 1.0f) * factorl;
+                g = log(g + 1.0f) * factorl;
+                b = log(b + 1.0f) * factorl;
+            }
+            ro = (r > k) ? 255 : 0;
+            go = (g > k) ? 255 : 0;
+            bo = (b > k) ? 255 : 0;
+            row[x] = qRgb(ro, go, bo);
+        }
     }
-    painter.end();
-    // flip, because Y axis has reverse direction in QImage
-    QTransform tfm;
-    tfm.rotate(180, Qt::XAxis);
-    return hist_img.transformed(tfm);
+    return hist_img;
 }
 
 
 //--------- **************** Histogram Dialog ****************---------
 HistogramDialog:: HistogramDialog(QWidget *parent, QImage &image) : QDialog(parent)
 {
-    this->setWindowTitle("R G B and Luminance(Y) Histogram");
+    this->setWindowTitle("R G B Histogram");
     this->resize(540, 400);
 
-    QGridLayout *gridLayout = new QGridLayout(this);
+    gridLayout = new QGridLayout(this);
 
     histLabel = new QLabel(this);
     histLabel->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
     gridLayout->addWidget(histLabel, 0, 0, 1, 2);
     // container for holding buttons
-    QWidget *container = new QWidget(this);
+    container = new QWidget(this);
     gridLayout->addWidget(container, 1, 0, 1, 1);
 
-    QDialogButtonBox *buttonBox = new QDialogButtonBox(Qt::Horizontal, this);
+    buttonBox = new QDialogButtonBox(Qt::Horizontal, this);
     buttonBox->setStandardButtons(QDialogButtonBox::Close);
     gridLayout->addWidget(buttonBox, 1, 1, 1, 1);
 
-    QHBoxLayout *hLayout = new QHBoxLayout(container);
+    hLayout = new QHBoxLayout(container);
     container->setLayout(hLayout);
 
-    QCheckBox *logBtn = new QCheckBox("Logarithmic", this);
+    logBtn = new QCheckBox("Logarithmic", this);
     hLayout->addWidget(logBtn);
 
     connect(logBtn, SIGNAL(clicked(bool)), this, SLOT(drawHistogram(bool)));
     connect(buttonBox, SIGNAL(accepted()), this, SLOT(accept()));
     connect(buttonBox, SIGNAL(rejected()), this, SLOT(reject()));
 
     // generate histograms
-    getHistogram(image, hist_r, hist_g, hist_b, hist_y);
+    getHistogram(image, hist_r, hist_g, hist_b);
     drawHistogram(false);
 }
 
-void
-HistogramDialog:: drawHistogram(bool logarithmic)
+void HistogramDialog:: drawHistogram(bool logarithmic)
 {
-    int hist_w = 256;
-    int hist_h = 160;
-    QImage imgR, imgG, imgB, imgY;
-    if (not logarithmic) {
-        imgR = histogramImage(hist_r, Qt::red, hist_w, hist_h);
-        imgG = histogramImage(hist_g, Qt::green, hist_w, hist_h);
-        imgB = histogramImage(hist_b, Qt::blue, hist_w, hist_h);
-        imgY = histogramImage(hist_y, QColor(127,127,127), hist_w, hist_h);
-    }
-    else { // logarithmic histograms
-        double loghist[4][256] = {};
-        for (int i=0; i<256; i++) {
-            loghist[0][i] = log(hist_r[i]);
-            loghist[1][i] = log(hist_g[i]);
-            loghist[2][i] = log(hist_b[i]);
-            loghist[3][i] = log(hist_y[i]);
-        }
-        imgR = histogramImage(loghist[0], Qt::red, hist_w, hist_h);
-        imgG = histogramImage(loghist[1], Qt::green, hist_w, hist_h);
-        imgB = histogramImage(loghist[2], Qt::blue, hist_w, hist_h);
-        imgY = histogramImage(loghist[3], QColor(127,127,127), hist_w, hist_h);
-    }
-
-    QImage img(hist_w*2+3, hist_h*2+3, QImage::Format_RGB32);
-    img.fill(Qt::white);
-    QPainter painter(&img);
-    painter.drawImage(0, 0, imgR);
-    painter.drawImage(hist_w+1, 0, imgG);
-    painter.drawImage(0, hist_h+1, imgB);
-    painter.drawImage(hist_w+1, hist_h+1, imgY);
-    painter.end();
+    int hist_w = 512;
+    int hist_h = 320;
+    QImage img;
+    img = histogramImage(hist_r, hist_g, hist_b, hist_w, hist_h, logarithmic);
 
     histLabel->setPixmap(QPixmap::fromImage(img));
 }

src/tools/histogram-viewer/histogram_viewer.h

@@ -1,7 +1,12 @@
 #pragma once
 #include "plugin.h"
+#include <cmath>
 #include <QDialog>
 #include <QLabel>
+#include <QGridLayout>
+#include <QHBoxLayout>
+#include <QCheckBox>
+#include <QDialogButtonBox>
 
 class ToolPlugin : public QObject, Plugin
 {
@@ -27,8 +32,12 @@ class HistogramDialog : public QDialog
     uint hist_r[256] = {};
     uint hist_g[256] = {};
     uint hist_b[256] = {};
-    uint hist_y[256] = {};
     //widgets
+    QGridLayout *gridLayout;
+    QWidget *container;
+    QDialogButtonBox *buttonBox;
+    QHBoxLayout *hLayout;
+    QCheckBox *logBtn;
     QLabel *histLabel;
 
     HistogramDialog(QWidget *parent, QImage &image);