Set default document res to 6K. Implement blending on canvas, mixer and export equirect.

src/canvas.h

@@ -8,7 +8,7 @@
 #include "canvas_modes.h"
 #include <stack>
 
-#define CANVAS_RES 512
+#define CANVAS_RES 1536
 
 class Layer
 {
@@ -20,7 +20,7 @@ public:
     bool m_alpha_locked = false;
     float m_opacity = 1.f;
     bool m_hightlight = false;
-    bool m_blend_mode = 0;
+    int m_blend_mode = 0;
     std::string m_name;
     int w = 0;
     int h = 0;