Data commit

Task/Grayscale-image/REXX/grayscale-image.rexx

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+/*REXX program converts a  RGB (red─green─blue) image into a  grayscale/greyscale image.*/
+  blue= '00 00 ff'x                              /*define the blue color  (hexadecimal).*/
+    @.= blue                                     /*set the entire  image  to blue color.*/
+ width=  60                                      /* width of the   image  (in pixels).  */
+height= 100                                      /*height  "  "      "      "   "       */
+
+  do    col=1  for width
+     do row=1  for height                        /* [↓]  C2D  convert  char ───► decimal*/
+     r= left(@.col.row, 1)      ;     r= c2d(r)  /*extract the component red  & convert.*/
+     g= substr(@.col.row, 2, 1) ;     g= c2d(g)  /*   "     "      "    green "    "    */
+     b=  right(@.col.row, 1)    ;     b= c2d(b)  /*   "     "      "    blue  "    "    */
+     _= d2c( (.2126*r + .7152*g + .0722*b) % 1)  /*convert RGB number  ───►  grayscale. */
+     @.col.row= copies(_, 3)                     /*redefine old RGB    ───►  grayscale. */
+     end   /*row*/                               /* [↑]  D2C  convert  decimal ───► char*/
+  end      /*col*/                               /* [↑]  x%1   is the same as  TRUNC(x) */
+                                                 /*stick a fork in it,  we're all done. */