Get the value of a specific pixel in an image?

If you want to segment an image, you need to know the values of the pixels in the image. To access a pixel you can use the methods: "Fct_Pixel_Get_GLI()" to get the GLI value, and "Fct_Pixel_Get_TAG()" to get the current TAG value. These methods require a pointer to the Tomo_Image pointer of the image associated with the frame (the frame->m_ima pointer) and the position of the pixel in the image.

Here is an example of the use of these functions (from the Pixel_Info tool).

#include "sliceO_include.hpp"

// ----------------------------------------------------------------------------

// Tool_Pixel_Update_Val

// Param: (char *) str_1 Pointer to a text representing the GLI value

// (char *) str_1 Pointer to a text representing the TAG value

// (SliceO_Frame *) frame Pointer to the desired frame

// Point_2D *) pos Position of the desired pixel in the frame

// Return: (void)

// ----------------------------------------------------------------------------

void Tool_Pixel_Update_Val( char *str1, char *str2, SliceO_Frame *frame, Point_2D *pos )

{

if ( ! frame ) {

sprintf( str1, "GLI: ----" ) ;

sprintf( str2, "Tag ---" ) ;

return ;

}

// --- transform 2D pos in 4D info ---

Vect v_pos ;

v_pos.set( (*pos)[0], (*pos)[1], frame->m_z, frame->m_t ) ;

// --- Get the GLI pixel value ---

int GLI_val = frame->Fct_Pixel_Get_GLI( frame, frame->m_ima, v_pos ) ;

// --- make sure the value is valid ---

if ( GLI_val == PIXEL_GLI_INVALID ) {

sprintf( str1, "invalid" ) ;

sprintf( str2, "invalid" ) ;

return ;

}

if ( GLI_val == PIXEL_GLI_OUTSIDE ) {

sprintf( str1, "outside" ) ;

sprintf( str2, "outside" ) ;

return ;

}

// --- special case for RGB images ---

if ( frame->m_pix_type & DATA_TYPE_COLOR ) {

Color val_col ;

val_col.color = GLI_val ;

sprintf( str1, "%3d,%3d,%3d", val_col.col.R, val_col.col.G, val_col.col.B ) ;

return ;

}

// --- convert to floating point value ---

float GLI_float = Fct_GLI_2_Float( frame, GLI_val ) ;

if ( frame->m_pix_type & DATA_TYPE_32BIT )

sprintf( str1, "GLI: %11.4g", GLI_float ) ;

else

sprintf( str1, "GLI: %4.0f", GLI_float ) ;

// --- Get the TAG pixel value ---

unsigned char TAG_val = frame->Fct_Pixel_Get_TAG( frame, frame->m_ima, v_pos ) ;

sprintf( str2, "Tag: %3d", TAG_val ) ;

}