Some refactoring of common VU functions.

[nageru] / vu_common.cpp

diff --git a/vu_common.cpp b/vu_common.cpp
new file mode 100644 (file)
index 0000000..9a6a35a
--- /dev/null
+++ b/vu_common.cpp
@@ -0,0 +1,50 @@
+#include "vu_common.h"
+#include <math.h>
+#include <algorithm>
+
+using namespace std;
+
+int lufs_to_pos(float level_lu, int height)
+{       
+       const float min_level = 9.0f;    // y=0 is top of screen, so “min” is the loudest level.
+       const float max_level = -18.0f;
+
+       // Handle -inf.
+       if (level_lu < max_level) {
+               return height - 1;
+       }
+
+       int y = lrintf(height * (level_lu - min_level) / (max_level - min_level));
+       y = std::max(y, 0);
+       y = std::min(y, height - 1);
+       return y;
+}
+
+void draw_vu_meter(QPainter &painter, float level_lu, int width, int height, int margin)
+{
+       painter.fillRect(margin, 0, width - 2 * margin, height, Qt::black);
+
+       // TODO: QLinearGradient is not gamma-correct; we might want to correct for that.
+       QLinearGradient on(0, 0, 0, height);
+       on.setColorAt(0.0f, QColor(255, 0, 0));
+       on.setColorAt(0.5f, QColor(255, 255, 0));
+       on.setColorAt(1.0f, QColor(0, 255, 0));
+       QColor off(80, 80, 80);
+
+       int y = lufs_to_pos(level_lu, height);
+
+       // Draw bars colored up until the level, then gray from there.
+       for (int level = -18; level < 9; ++level) {
+               int min_y = lufs_to_pos(level + 1.0f, height) + 1;
+               int max_y = lufs_to_pos(level, height) - 1;
+
+               if (y > max_y) {
+                       painter.fillRect(margin, min_y, width - 2 * margin, max_y - min_y, off);
+               } else if (y < min_y) {
+                       painter.fillRect(margin, min_y, width - 2 * margin, max_y - min_y, on);
+               } else {
+                       painter.fillRect(margin, min_y, width - 2 * margin, y - min_y, off);
+                       painter.fillRect(margin, y, width - 2 * margin, max_y - y, on);
+               }
+       }
+}