git.sesse.net Git - nageru/blob - vu_common.cpp

   1 #include "vu_common.h"
   2
   3 #include <QColor>
   4 #include <QPainter>
   5 #include <algorithm>
   6 #include <cmath>
   7
   8 using namespace std;
   9
  10 double lufs_to_pos(float level_lu, int height, float min_level, float max_level)
  11 {
  12         // Note: “max” is the loudest level, but y=0 is top of screen.
  13
  14         // Handle -inf.
  15         if (level_lu < min_level) {
  16                 return height - 1;
  17         }
  18
  19         double y = height * (level_lu - max_level) / (min_level - max_level);
  20         y = max<double>(y, 0);
  21         y = min<double>(y, height - 1);
  22
  23         // If we are big enough, snap to pixel grid instead of antialiasing
  24         // the edges; the unevenness will be less noticeable than the blurriness.
  25         double height_per_level = height / (max_level - min_level) - 2.0;
  26         if (height_per_level >= 10.0) {
  27                 y = round(y);
  28         }
  29
  30         return y;
  31 }
  32
  33 void draw_vu_meter(QPainter &painter, int width, int height, int horizontal_margin, double segment_margin, bool is_on, float min_level, float max_level, bool flip, int y_offset)
  34 {
  35         painter.fillRect(horizontal_margin, y_offset, width - 2 * horizontal_margin, height, Qt::black);
  36
  37         for (int y = 0; y < height; ++y) {
  38                 // Find coverage of “on” rectangles in this pixel row.
  39                 double coverage = 0.0;
  40                 for (int level = floor(min_level); level <= ceil(max_level); ++level) {
  41                         double min_y = lufs_to_pos(level + 1.0, height, min_level, max_level) + segment_margin * 0.5;
  42                         double max_y = lufs_to_pos(level, height, min_level, max_level) - segment_margin * 0.5;
  43                         min_y = std::max<double>(min_y, y);
  44                         min_y = std::min<double>(min_y, y + 1);
  45                         max_y = std::max<double>(max_y, y);
  46                         max_y = std::min<double>(max_y, y + 1);
  47                         coverage += max_y - min_y;
  48                 }
  49
  50                 double on_r, on_g, on_b;
  51                 if (is_on) {
  52                         double t = double(y) / height;
  53                         if (t <= 0.5) {
  54                                 on_r = 1.0;
  55                                 on_g = 2.0 * t;
  56                                 on_b = 0.0;
  57                         } else {
  58                                 on_r = 1.0 - 2.0 * (t - 0.5);
  59                                 on_g = 1.0;
  60                                 on_b = 0.0;
  61                         }
  62                 } else {
  63                         on_r = on_g = on_b = 0.05;
  64                 }
  65
  66                 // Correct for coverage and do a simple gamma correction.
  67                 int r = lrintf(255 * pow(on_r * coverage, 1.0 / 2.2));
  68                 int g = lrintf(255 * pow(on_g * coverage, 1.0 / 2.2));
  69                 int b = lrintf(255 * pow(on_b * coverage, 1.0 / 2.2));
  70                 int draw_y = flip ? (height - y - 1) : y;
  71                 painter.fillRect(horizontal_margin, draw_y + y_offset, width - 2 * horizontal_margin, 1, QColor(r, g, b));
  72         }
  73 }