How can I save a patch as an image?

I'm working on a project that evolves a population of polygons using differential evolution to approximate an image. I have an objective function, or "fitness function" that I'm minimizing based on the difference between the original image and the image approximated using polygons at each pixel of the image. The problem I am encountering occurs when I try to save the patch I create as an MxNx3 matrix representing the image.

   function [fitness]=fitnessFunction5(dnaPolygonCollection,y)%,generatedImage)

%fitnessFunction(sourceImage,generatedImage) 
%a function used to calculate the fit of an approximated image

global sourceImage numVertices numPolygons;

[imgY,imgX,numberOfColorChannelsA] = size(sourceImage); 

generatedImage=...
    internalDrawRealPolygonImage(dnaPolygonCollection, imgX, imgY,...
    numVertices, numPolygons);

deltaRGB=(abs(double(sourceImage)-double(generatedImage)));

fitness=sum(sum(sum(deltaRGB)));

end

      function [ newImage ]=...
          internalDrawRealPolygonImage( dnaPolygonCollection, imgX, imgY,...
          numVertices, numPolygons )

          resizedDNA=reshape(dnaPolygonCollection,(4+(2*numVertices)),numPolygons);
          resizedDNA=resizedDNA';

          XVertices=zeros(numPolygons,numVertices);
          YVertices=zeros(numPolygons,numVertices);

          colorData=floor(resizedDNA(:,1:3)*255);
          colorData2=resizedDNA(:,1:3);

          alphaData=resizedDNA(:,4);
          XVertices=floor(resizedDNA(:,5:2:end)*imgX);
          YVertices=floor(resizedDNA(:,6:2:end)*imgY);

          XVertices=XVertices';
          YVertices=YVertices';

          p=patch('XData',XVertices,'YData',YVertices,...
          'FaceColor','flat','FaceVertexCData',colorData2,...
          'AlphaDataMapping','none','FaceVertexAlphaData',alphaData,'EdgeAlpha',0);

          I = getframe(gcf);
          newImage=imresize(I.cdata, [imgY,imgX]);

          delete(p);
          cla;
      end

the image created by saving the color information from the call to getframe(gcf) does not change, so the fitness value never changes. Is there something wrong with the way I am attempting to retrieve the color information from the current figure? Why is the image not updated?

[Walter Roberson]

Experiment with putting a drawnow() before the getframe(). It should not be necessary in theory but in practice sometimes it is. Sometimes it is not long enough and you need to pause() a short bit instead.