Axis x,y value to pixcel ?!

I have 3 matrix lat/long and c as my other parameter. I need to find the c value for a given lat/long. Since lat/long are a matrix of 1200 pixels, I need to plot them and then use a line function to find the desired position on the image, my code is shown below. Instead of using [x y]= ginput (1), which requires a pointer, I use my line result to find the position of the point on the axes. But I can't use the impixelinfo function, and axes2pix doesn't work for me either. So is there any way to just extract the c value for a point on the plot based on the axis coordinate!!!! Or convert the axis coordinates to pixcel values and from there find the c value from the matrix?!!!

m_pcolor(S.lon, S.lat, S.im) % lat = S.lat; lon = S.lon; c = S.im;
t= m_line(-35.852379,-74.960411,'marker','o','markerfacecolor','r','linewidth',0.5,'MarkerEdgeColor','r', 'linest','none','MarkerSize',8);%, 'MarkerEdgeColor','k'
x = -0.1546; y = 0.2140   % XData: -0.1546 ; YData: 0.2140   % how to convert to pixcel value?!
[filonx,filaty] = m_xy2ll(x,y)  %filonx = -35.8455 ; filaty = -74.9607
% but C??
% % % for extra over view 
% t = 
%   Line (m_line) with properties:
% 
%               Color: [0 0.4470 0.7410]
%           LineStyle: 'none'
%           LineWidth: 0.5000
%              Marker: 'o'
%          MarkerSize: 8
%     MarkerFaceColor: [1 0 0]
%               XData: -0.1546
%               YData: 0.2140
%               ZData: [1×0 double]