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#import "OpenGLMotionBlur.h"
 
#define ALPHA 0.6
#define TEX_W 512
#define TEX_H 512
 
@implementation OpenGLMotionBlur
 
- (id)init {
  self = [super init];
  alpha = ALPHA;
  width = TEX_W;
  height = TEX_H;
  bitmapData = (unsigned char *)malloc( width*height*3*sizeof( unsigned char ) );
  glGenTextures( 1, texName );
  glBindTexture( GL_TEXTURE_2D, texName[0] );
  glTexImage2D(
    GL_TEXTURE_2D, 0 , GL_RGB, width, height,
    0, GL_RGB, GL_UNSIGNED_BYTE, bitmapData
  );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  return self;
}
 
- (void)dealloc {
  free( bitmapData );
  [super dealloc];
}
 
- (void)setViewOrtho {
  glMatrixMode( GL_PROJECTION );
  glPushMatrix();
  glLoadIdentity();  
  glOrtho( 0, 1, 0, 1,  -1, 1 );
  glMatrixMode( GL_MODELVIEW );
  glPushMatrix();
  glLoadIdentity();  
}
 
- (void)drawTexture {
  glBindTexture( GL_TEXTURE_2D, texName[0] );
  glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
  glEnable( GL_BLEND );
  glEnable( GL_TEXTURE_2D );
  glColor4f( 1.0, 1.0, 1.0, alpha );
  glBegin( GL_POLYGON );
  glTexCoord2f( 0.0f, 0.0f );
  glVertex2f( 0, 0 );
  glTexCoord2f( 0.0f, 1.0f );
  glVertex2f( 0, 1 );
  glTexCoord2f( 1.0f, 1.0f );
  glVertex2f( 1, 1 );
  glTexCoord2f( 1.0f, 0.0f );
  glVertex2f( 1, 0 );
  glEnd();
}
 
- (void)start {
  glViewport( 0, 0, width, height );
  [self setViewOrtho];
  [self drawTexture];
}
 
- (void)end {
  glBindTexture( GL_TEXTURE_2D, texName[0] );
  glCopyTexImage2D(
    GL_TEXTURE_2D,
    0,
    GL_RGB,
    0, 0,
    width, height,
    0
  );
}
 
- (void)draw {
  [self setViewOrtho];
  [self drawTexture];
}
 
- (unsigned char *)bitmapData {
  return bitmapData;
}
 
- (void)setWidth:(int)w height:(int)h {
  width = w;
  height = h;
  free( bitmapData );
  bitmapData = (unsigned char *)malloc( width*height*3*sizeof( unsigned char ) );
  glBindTexture( GL_TEXTURE_2D, texName[0] );
  glTexImage2D(
    GL_TEXTURE_2D, 0 , GL_RGB, width, height,
    0, GL_RGB, GL_UNSIGNED_BYTE, bitmapData
  );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
}
 
- (int)width {
  return width;
}
 
- (int)height {
  return height;
}
 
- (void)setAlpha:(float)a {
  alpha = a;
}
 
- (float)alpha {
  return alpha;
}
 
@end