add jpg library, export as jpg, export animation frames, add pressure support on mac

libs/jpeg/timer.h

@@ -0,0 +1,40 @@
+// File: timer.h
+#pragma once
+
+typedef unsigned long long timer_ticks;
+
+class timer
+{
+public:
+   timer();
+   timer(timer_ticks start_ticks);
+
+   void start();
+   void start(timer_ticks start_ticks);
+
+   void stop();
+
+   double get_elapsed_secs() const;
+   inline double get_elapsed_ms() const { return get_elapsed_secs() * 1000.0f; }
+   timer_ticks get_elapsed_us() const;
+
+   static void init();
+   static inline timer_ticks get_ticks_per_sec() { return g_freq; }
+   static timer_ticks get_init_ticks();
+   static timer_ticks get_ticks();
+   static double ticks_to_secs(timer_ticks ticks);
+   static inline double ticks_to_ms(timer_ticks ticks) { return ticks_to_secs(ticks) * 1000.0f; }
+   static inline double get_secs() { return ticks_to_secs(get_ticks()); }
+   static inline double get_ms() { return ticks_to_ms(get_ticks()); }
+
+private:
+   static timer_ticks g_init_ticks;
+   static timer_ticks g_freq;
+   static double g_inv_freq;
+
+   timer_ticks m_start_time;
+   timer_ticks m_stop_time;
+
+   bool m_started : 1;
+   bool m_stopped : 1;
+};