int IPReadFile(char *filename, image img);         // Read PNM file
int IPWriteFile(char *filename, image img);        // Write PNM file
int IPLaplace (grayimage imgIn, grayimage imgOut); // Laplace edge detection on gray image
int IPSobel (grayimage imageIn, grayimage imgOut); // Sobel edge detection on gray image
int IPColor2Gray (image imgIn,  grayimage imgOut); // Transfer color to gray image
int IPCol2HuePixel(color c);                       // Return hue form RGB pixel
color IPRGB2ColPixel(BYTE R, BYTE G, BYTE B);      // Return color from RGB pixel
int IPRCol2Hue(image img, graymage hue, grayimage sat, grayimage ity);// Transform RGB image to HSI image
int IPRGB2Col(grayimage r, grayimage g, grayimage b, image out);      // Transform 3*gray to color image