RGB coarse scaler

Simple sample to show you how to coarse scale an image using hardware.

Using library

GP2X minimal library by rlyeh, 2005

License

• Free for non-commercial projects (it would be nice receiving a mail from you).  Other cases, ask me first.
• GamePark Holdings is not allowed to use this library and/or use parts from it.

Source code

#include "minimal.h"

int main(int argc, char *argv[])
{
 int i, j;

 gp2x_init(1000, 15, 11025,16,1,60, 1);

 //put a 32x32 bitmap at (0,0) coordiantes of screen
 for(j=0;j<32;j++)
  for(i=0;i<32;i++)
   gp2x_video_RGB[0].screen16[i+j*320]=gp2x_video_RGB_color15(i*8,j*8,i*4+j*4,0);

 //show image
 gp2x_video_RGB_flip(0);

 while(1)
 {
  unsigned long  pad=gp2x_joystick_read();
  static unsigned char scaled=0;

  if(pad & GP2X_VOL_DOWN) if(pad & GP2X_START) exit(0);

  //enable 32x32 image to fit the 320x240 display area (aka, enable scaling)
  if(pad & GP2X_A) gp2x_video_RGB_setscaling(32,32);

  //enable 320x240 image to fit the 320x240 display area (aka, disable scaling)
  if(pad & GP2X_B) gp2x_video_RGB_setscaling(320,240);
 }
}

void gp2x_sound_frame(void *blah, void *buff, int samples) { }

Explanation

• Our gp2x_init line inits the whole library.  We set 1000 ticks per second, 15 bits video mode, 11025/16bits/stereo/60Hz sound mode, and solid font.
• Our gp2x_joystick_read line reads the joystick.  It is used to act properly to different button combinations.
• Our gp2x_video_RGB [0].screen16, gp2x_video_RGB_color15 line sets a bitmap into (0,0) coordinates.
• Our gp2x_video_RGB_flip line updates the screen and our gp2x_video_RGB [0].screen16 pointer for next frame.
• Our gp2x_video_RGB_setscaling lines enable or disable RGB scaling.
• Our gp2x_sound_frame line fills our sound buffer.  Note that this function will not generate any sound since we have written a void function.

C Compilation

arm-linux-gcc minimal.c scaler.c -static -lpthread -lm

C++ Compilation

arm-linux-g++ minimal.c scaler.c -static -lpthread -lm

Output

• this program shows a 32x32 bitmap at (0,0) coordinates.
• press A to enable fullscreen coarse scaling.
• press B to disable fullscreen coarse scaling.
• press volume down and start buttons to exit.