Retrieve a value from a run of pixels
int PiGetPixelFromData( char const *data, int type, unsigned short pixel, unsigned long *value );
This function is similar to PiGetPixel(), except that PiGetPixelFromData() retrieves the value from a run of pixels pointed to by data, instead of from an image. The type argument indicates the format of the data and must correspond to one of the supported image types, as listed for PhImage_t. The pixel argument is the index of the pixel into the run of data, and value points to an area where you want the result to be stored.
PhImage_t, PiGetPixel(), PiGetPixelRGB(), PiSetPixel(), PiSetPixelInData()
“Images” in the Raw Drawing and Animation chapter of the Photon Programmer's Guide