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;
+double lufs_to_pos(float level_lu, int height, float min_level, float max_level)
+{
+ // Note: “max” is the loudest level, but y=0 is top of screen.
// Handle -inf.
- if (level_lu < max_level) {
+ if (level_lu < min_level) {
return height - 1;
}
- int y = lrintf(height * (level_lu - min_level) / (max_level - min_level));
- y = max(y, 0);
- y = min(y, height - 1);
+ double y = height * (level_lu - max_level) / (min_level - max_level);
+ y = max<double>(y, 0);
+ y = min<double>(y, height - 1);
+
+ // If we are big enough, snap to pixel grid instead of antialiasing
+ // the edges; the unevenness will be less noticeable than the blurriness.
+ double height_per_level = height / (max_level - min_level) - 2.0;
+ if (height_per_level >= 10.0) {
+ y = round(y);
+ }
+
return y;
}
-void draw_vu_meter(QPainter &painter, int width, int height, int margin, bool is_on)
+void draw_vu_meter(QPainter &painter, int width, int height, int margin, bool is_on, float min_level, float max_level, bool flip)
{
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);
-
- // 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;
+ for (int y = 0; y < height; ++y) {
+ // Find coverage of “on” rectangles in this pixel row.
+ double coverage = 0.0;
+ for (int level = floor(min_level); level <= ceil(max_level); ++level) {
+ double min_y = lufs_to_pos(level + 1.0, height, min_level, max_level) + 1.0;
+ double max_y = lufs_to_pos(level, height, min_level, max_level) - 1.0;
+ min_y = std::max<double>(min_y, y);
+ min_y = std::min<double>(min_y, y + 1);
+ max_y = std::max<double>(max_y, y);
+ max_y = std::min<double>(max_y, y + 1);
+ coverage += max_y - min_y;
+ }
+ double on_r, on_g, on_b;
if (is_on) {
- painter.fillRect(margin, min_y, width - 2 * margin, max_y - min_y, on);
+ double t = double(y) / height;
+ if (t <= 0.5) {
+ on_r = 1.0;
+ on_g = 2.0 * t;
+ on_b = 0.0;
+ } else {
+ on_r = 1.0 - 2.0 * (t - 0.5);
+ on_g = 1.0;
+ on_b = 0.0;
+ }
} else {
- painter.fillRect(margin, min_y, width - 2 * margin, max_y - min_y, off);
+ on_r = on_g = on_b = 0.05;
}
+
+ // Correct for coverage and do a simple gamma correction.
+ int r = lrintf(255 * pow(on_r * coverage, 1.0 / 2.2));
+ int g = lrintf(255 * pow(on_g * coverage, 1.0 / 2.2));
+ int b = lrintf(255 * pow(on_b * coverage, 1.0 / 2.2));
+ int draw_y = flip ? (height - y - 1) : y;
+ painter.fillRect(margin, draw_y, width - 2 * margin, 1, QColor(r, g, b));
}
}