+#include "rgb_histogram.h"
+
+#include <QPainter>
+#include <QRect>
+
+class QPaintEvent;
+class QResizeEvent;
+
+using namespace std;
+
+static constexpr int margin_left = 16;
+static constexpr int margin_top = 14;
+static constexpr int margin_right = 14;
+static constexpr int margin_bottom = 25;
+
+RGBHistogram::RGBHistogram(QWidget *parent)
+ : QWidget(parent), red(256, 0.0), green(256, 0.0), blue(256, 0.0)
+{
+}
+
+void RGBHistogram::set_histograms(std::vector<double> red, std::vector<double> green, std::vector<double> blue)
+{
+ assert(red.size() == 256);
+ assert(green.size() == 256);
+ assert(blue.size() == 256);
+ this->red = std::move(red);
+ this->green = std::move(green);
+ this->blue = std::move(blue);
+ repaint();
+}
+
+void RGBHistogram::paintEvent(QPaintEvent *event)
+{
+ QPainter painter(this);
+ painter.fillRect(0, 0, width(), height(), Qt::white);
+ painter.setRenderHints(QPainter::Antialiasing);
+
+ double max = 0.0;
+ for (unsigned i = 0; i < 256; ++i) {
+ max = std::max(max, red[i]);
+ max = std::max(max, green[i]);
+ max = std::max(max, blue[i]);
+ }
+
+ // Draw the graphs. (We'd like to get rid of the bottom line, but that's just cosmetic.)
+ painter.setPen(QPen(Qt::red));
+ painter.setBrush(QBrush(QColor(255, 127, 127, 80)));
+ draw(red, max, Qt::GlobalColor::red, &painter);
+
+ painter.setPen(QPen(Qt::green));
+ painter.setBrush(QBrush(QColor(127, 255, 127, 80)));
+ draw(green, max, Qt::GlobalColor::green, &painter);
+
+ painter.setPen(QPen(Qt::blue));
+ painter.setBrush(QBrush(QColor(127, 127, 255, 80)));
+ draw(blue, max, Qt::GlobalColor::blue, &painter);
+
+ // Draw the tick lines.
+ int w = (width() - 1) - margin_left - margin_right;
+ painter.setPen(QPen(Qt::black));
+ painter.setBrush(QBrush());
+ for (int i = 0; i < 256; i += 10) {
+ int th = (i % 50 == 0) ? 5 : 2;
+ double x = (i / 255.0) * w + margin_left;
+ double y = (height() - 1) - margin_top - margin_bottom;
+ painter.drawLine(QPointF(x, y + margin_top), QPointF(x, y + margin_top - th));
+ }
+
+ // And the axis labels.
+ for (int i = 0; i < 256; i += 50) {
+ char buf[16];
+ snprintf(buf, sizeof(buf), "%d", i);
+
+ double x = (i / 255.0) * w + margin_left;
+ double y = (height() - 1) - margin_top - margin_bottom;
+ painter.drawText(QRectF(x - 20, y + margin_top, 40, margin_bottom), Qt::AlignCenter | Qt::AlignTop, QString(buf));
+ }
+}
+
+void RGBHistogram::draw(const vector<double> &v, double max, Qt::GlobalColor color, QPainter *painter)
+{
+ int w = (width() - 1) - margin_left - margin_right;
+ int h = (height() - 1) - margin_top - margin_bottom;
+
+ QPointF points[258];
+ points[0] = QPointF(margin_left, margin_top + h);
+ for (int i = 0; i < 256; ++i) {
+ double x = (i / 255.0) * w + margin_left;
+ double y = (1.0 - (v[i] / max)) * h + margin_top;
+ points[i + 1] = QPointF(x, y);
+ }
+ points[257] = QPointF(margin_left + w, margin_top + h);
+ painter->drawPolygon(points, 258);
+}