Data commit

Task/Bitmap-Histogram/Zkl/bitmap-histogram-1.zkl

@@ -0,0 +1,14 @@
+fcn histogram(image){
+   hist:=List.createLong(256,0);	// array[256] of zero
+   image.data.howza(0).pump(Void,'wrap(c){ hist[c]+=1 });  // byte by byte loop
+   hist;
+}
+fcn histogramMedian(hist){
+   from,to:=0,(2).pow(8) - 1; // 16 bits of luminance
+   left,right:=hist[from],hist[to];
+   while(from!=to){
+      if(left<right){ from+=1; left +=hist[from]; }
+      else 	    { to  -=1; right+=hist[to];   }
+   }
+   from
+}

Task/Bitmap-Histogram/Zkl/bitmap-histogram-2.zkl

@@ -0,0 +1,10 @@
+img:=PPM.readPPMFile("lenaGrey.ppm"); // a grey scale image
+median:=histogramMedian(histogram(img));
+median.println();
+
+bw:=PPM(img.w,img.h);
+  // stream bytes from orginal, convert to black/white, write to new image
+  // each pixel is 24 bit RGB
+img.data.pump(bw.data.clear(),'wrap(c){ if(c>median) 0xff else 0  });
+
+bw.write(File("foo.ppm","wb"));