From 340aafea6720e684a884c5f8da9762d033f2dad0 Mon Sep 17 00:00:00 2001
From: David Rose <david@ddrose.com>
Date: Sun, 8 Nov 2009 03:11:32 +0000
Subject: [PATCH] add copy_channel

---
 panda/src/pnmimage/pnmImage.cxx | 53 +++++++++++++++++++++++++++++++++
 panda/src/pnmimage/pnmImage.h   |  3 ++
 2 files changed, 56 insertions(+)

diff --git a/panda/src/pnmimage/pnmImage.cxx b/panda/src/pnmimage/pnmImage.cxx
index b4b27a2e02..a65bd8805e 100644
--- a/panda/src/pnmimage/pnmImage.cxx
+++ b/panda/src/pnmimage/pnmImage.cxx
@@ -900,6 +900,59 @@ lighten_sub_image(const PNMImage &copy, int xto, int yto,
   }
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: PNMImage::copy_channel
+//       Access: Published
+//  Description: Copies just a single channel from the source image
+//               into a single channel of this image, leaving the
+//               remaining channels alone.
+////////////////////////////////////////////////////////////////////
+void PNMImage::
+copy_channel(const PNMImage &copy, int xto, int yto, int cto,
+             int xfrom, int yfrom, int cfrom,
+             int x_size, int y_size) {
+  int xmin, ymin, xmax, ymax;
+  setup_sub_image(copy, xto, yto, xfrom, yfrom, x_size, y_size,
+                  xmin, ymin, xmax, ymax);
+
+  if (get_maxval() == copy.get_maxval()) {
+    // The simple case: no pixel value rescaling is required.
+    int x, y;
+    for (y = ymin; y < ymax; y++) {
+      if (cto == 3 && cfrom == 3) {
+        // To alpha channel, from alpha channel.
+        for (x = xmin; x < xmax; x++) {
+          set_alpha_val(x, y, copy.get_alpha_val(x - xmin + xfrom, y - ymin + yfrom));
+        }
+      } else if (cto == 3 && cfrom == 0) {
+        // To alpha channel, from blue (or gray) channel.
+        for (x = xmin; x < xmax; x++) {
+          set_alpha_val(x, y, copy.get_blue_val(x - xmin + xfrom, y - ymin + yfrom));
+        }
+      } else if (cto == 0 && cfrom == 3) {
+        // To blue (or gray) channel, from alpha channel.
+        for (x = xmin; x < xmax; x++) {
+          set_blue_val(x, y, copy.get_alpha_val(x - xmin + xfrom, y - ymin + yfrom));
+        }
+      } else {
+        // Generic channels.
+        for (x = xmin; x < xmax; x++) {
+          set_channel_val(x, y, cto, copy.get_channel_val(x - xmin + xfrom, y - ymin + yfrom, cfrom));
+        }
+      }
+    }
+
+  } else {
+    // The harder case: rescale pixel values according to maxval.
+    int x, y;
+    for (y = ymin; y < ymax; y++) {
+      for (x = xmin; x < xmax; x++) {
+        set_channel(x, y, cto, copy.get_channel(x - xmin + xfrom, y - ymin + yfrom, cfrom));
+      }
+    }
+  }
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: PNMImage::render_spot
 //       Access: Published
diff --git a/panda/src/pnmimage/pnmImage.h b/panda/src/pnmimage/pnmImage.h
index ff3b180653..f5a7fdcbf8 100644
--- a/panda/src/pnmimage/pnmImage.h
+++ b/panda/src/pnmimage/pnmImage.h
@@ -203,6 +203,9 @@ PUBLISHED:
                          int xfrom = 0, int yfrom = 0,
                          int x_size = -1, int y_size = -1,
                          double pixel_scale = 1.0);
+  void copy_channel(const PNMImage &copy, int xto, int yto, int cto,
+                    int xfrom = 0, int yfrom = 0, int cfrom = 0,
+                    int x_size = -1, int y_size = -1);
 
   void render_spot(const Colord &fg, const Colord &bg,
                    double min_radius, double max_radius);