FIND LOCAL MAXIMA
I need an effective algorithm for finding local maxima in my Hough accumulator
the procedure HoughResultToParameterDyna
the procedure HoughResultToParameterDyna
///
/// Max_Array 2D Integer array , very simple scan through the hole array
///
function MAX_2D ( aHoughResult : THoughResult ) : Integer;
var n,m : Integer;
i,j : Integer;
max : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
max := aHoughResult[0][0];
for i:= 0 to n -1 do
for j := 0 to m-1 do
if aHoughResult[i][j] > max then
max :=aHoughResult[i][j];
result := max;
end;
///
/// MEAN_Array 2D Integer array
///
function MEAN_2D_Local ( aHoughResult : THoughResult; x_pos, y_pos, x_size, y_size : Integer ) : Integer;
var n,m : Integer;
i,j : Integer;
mean : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
mean := 0;
if ((x_pos>=(n-x_size)) or (y_pos>=(m-y_size))) then
begin
result := 0;
exit;
end;
for i:= x_pos to x_pos + x_size do
for j := y_pos to y_pos + y_size do
mean :=mean + aHoughResult[i][j];
result := round( mean / ((x_size+1) * (y_size+1))) ;
end;
///
/// MAX_Array 2D Integer array
///
function MAX_2D_Local ( aHoughResult : THoughResult; x_pos, y_pos, x_size, y_size : Integer ) : Integer;
var n,m : Integer;
i,j : Integer;
max : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
if ((x_pos>=(n-x_size)) or (y_pos>=(m-y_size))) then
begin
result := 0;
exit;
end;
max := aHoughResult[x_pos][y_pos];
for i:= x_pos to x_pos + x_size do
for j := y_pos to y_pos + y_size do
if aHoughResult[i][j] > max then
max :=aHoughResult[i][j];
result := max;
end;
///
/// Min_Array 2D Integer array
///
function MIN_2D ( aHoughResult : THoughResult ) : Integer;
var n,m : Integer;
i,j : Integer;
min : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
min := aHoughResult[0][0];
for i:= 0 to n -1 do
for j := 0 to m-1 do
if aHoughResult[i][j] < min then
min :=aHoughResult[i][j];
result := min;
end;
///
/// clear result array
///
function ResetArray (var aHoughResult : THoughResult ) : Integer;
var n,m : Integer;
i,j : Integer;
min : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
min := aHoughResult[0][0];
for i:= 0 to n -1 do
for j := 0 to m-1 do
aHoughResult[i][j] := 0 ;
result := 1;
end ;
///
/// copy the Hough Accumulator into a 3D INT Array Data type
/// in :
/// aHoughResult -> the Hough accu
/// range [ 0..1]
/// out:
/// aHoughFinal list of points above the max
/// [x,y,z]
///
///
procedure HoughResultToParameter(aHoughResult : THoughResult; Range : Real; var aHoughFinal : THoughFinal );
var n,m : Integer;
i,j : Integer;
xquer : Integer;
MAX : Integer;
MAXR : Real;
resultlen : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
resultlen := 0;
Max := MAX_2D(aHoughResult);
if ( max = 0) then max := 1 ;
MaxR := Max * Range;
for i:= 0 to n-1 do
for j:= 0 to m-1 do
if (aHoughResult[i,j] > MaxR ) then
begin
setlength (aHoughFinal, resultlen+1);
aHoughFinal[resultlen].x := i;
aHoughFinal[resultlen].y := j;
aHoughFinal[resultlen].z := aHoughResult[i,j];
resultlen := resultlen + 1;
end;
end;
///
/// as above, but now with dynamic thresholding
/// http://homepages.inf.ed.ac.uk/rbf/HIPR2/histeq.htm
/// http://homepages.inf.ed.ac.uk/rbf/HIPR2/hough.htm
///
///
procedure HoughResultToParameterDynamic(aHoughResult : THoughResult; Range : Real; var aHoughFinal : THoughFinal );
var n,m : Integer;
i,j : Integer;
xquer : Integer;
MAX : Integer;
Mean : Integer;
MAXR : Real;
resultlen : Integer;
Grad : Integer;
Grad_Min : Integer;
begin
n := length(aHoughResult);
m := length(aHoughResult[0]);
resultlen := 0;
Grad_Min := 30 ;
for i:= 0 to n-1 do
for j:= 0 to m-1 do
begin
Max := MAX_2D_Local (aHoughResult, i,j, 10, 10 );
mean := MEAN_2D_Local (aHoughResult, i,j, 10, 10 );
Grad := (Max - Mean);
MaxR := Max * Range;
if ((aHoughResult[i,j] > MaxR ) and (Grad > Grad_min)) then
begin
setlength (aHoughFinal, resultlen+1);
aHoughFinal[resultlen].x := i;
aHoughFinal[resultlen].y := j;
aHoughFinal[resultlen].z := aHoughResult[i,j];
aHoughFinal[resultlen].Z1 := Round(MaxR);
resultlen := resultlen + 1;
end;
end;
end;ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
how to find maxima with this algo ?
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
any chance for working pascal code for that problem ?
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
really missing some code i can immeadiatly follow - anyhow thanks for discussion
ASKER
I tried with the gradient F(x) - F(x+1) > threshold value , but this is not suffiecient as the peak is not a single point, sometimes a small area -
need something like image / line thinning in advance --
as the complete code is a Hough pattern recognition algo - any code reference how it is done here is helpful.
most of the hough code I found just take the Hough accu as it is ... this is fine for the demo but not for real images