none rectangular scissor boxes

[NeX]

Hi,

is it possible to make a cut out that is not rectangular? maybe using a polygon in some way?

[jamesbowman]

Yes! This example draws a background image, and then uses "Poly" to draw an octagon into the stencil buffer.
The StencilFunc() is then switched on so that only pixels inside the octagon shape are drawn.


#include <EEPROM.h>
#include <SPI.h>
#include <GD2.h>

void setup()
{
 GD.begin();
 GD.cmd_loadimage(0, 0);
 GD.load("tree.jpg");
}

void loop()
{
 GD.Clear();
 GD.Begin(BITMAPS);
 GD.Vertex2ii(0, 0);

 // Draw an octagon into the stencil buffer, stencil value 255
 GD.SaveContext();
 Poly po;
 po.begin();
 int centerx = 16 * 240, centery = 16 * 136;
 for (int i = 0; i < 8; i++) {
   int th = 0x2000 * i; // angle
   int r = 16 * 120;
   po.v(centerx + GD.rsin(r, th),
        centery + GD.rcos(r, th));
 }
 po.paint();
 GD.RestoreContext();

 // Now only draw pixels whose stencil is 255
 GD.StencilFunc(EQUAL, 255, 255);

 // Clear by drawing a black fullscreen rectangle
 GD.ColorRGB(0, 0, 0);
 GD.Begin(RECTS);
 GD.Vertex2ii(0, 0);
 GD.Vertex2ii(480, 272);

 // Taken from 'fizz'
 GD.Begin(POINTS);
 for (int i = 0; i < 100; i++) {
   GD.PointSize(GD.random(16 * 50));
   GD.ColorRGB(GD.random(256),
               GD.random(256),
               GD.random(256));
   GD.ColorA(GD.random(256));
   GD.Vertex2ii(GD.random(480), GD.random(272));
 }

 GD.swap();
}



[NeX]

Worked flawlessly as usual, thanks for the help!