# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1495144222 -7200
# Node ID 81ee57d5c0829e8c6a7e1fbf7cbf90d59d5e8076
# Parent  27660220db5a93774830afa973fa461493deddd5
Switched to using a I0RRGGBB colour representation.

diff -r 27660220db5a -r 81ee57d5c082 README.txt
--- a/README.txt	Thu May 18 01:58:26 2017 +0200
+++ b/README.txt	Thu May 18 23:50:22 2017 +0200
@@ -1,3 +1,26 @@
+Introduction
+------------
+
+The VGAPIC32 project provides software and circuit information to generate an
+analogue VGA signal from a PIC32 microcontroller.
+
+Contact, Copyright and Licence Information
+------------------------------------------
+
+The author can be contacted at the following e-mail address:
+
+paul@boddie.org.uk
+
+Copyright and licence information can be found in the docs directory - see
+docs/COPYING.txt and docs/gpl-3.0.txt for more information.
+
+
+
+Hardware Details
+================
+
+The pin usage of this solution is documented below.
+
 PIC32MX270F256B-50I/SP Pin Assignments
 --------------------------------------
 
@@ -21,14 +44,23 @@
 Data Signal Routing
 -------------------
 
-D7 -> 220R -> R
+For one bit of intensity, two bits per colour channel:
+
+D7 -> 2200R -> I
+
+I -> diode -> R -> diode -> D7
+I -> diode -> G -> diode -> D7
+I -> diode -> B -> diode -> D7
+
 D6 (not connected)
+
 D5 -> 470R -> R
-D4 -> 470R -> G
-D3 -> 1000R -> G
-D2 -> 2200R -> G
-D1 -> 220R -> B
-D0 -> 470R -> B
+D4 -> 1000R -> R
+D3 -> 470R -> G
+D2 -> 1000R -> G
+D1 -> 470R -> B
+D0 -> 1000R -> B
+
 HSYNC -> 3.3V:5V -> HS
 VSYNC -> 3.3V:5V -> VS
 
@@ -58,3 +90,5 @@
 http://papilio.cc/index.php?n=Papilio.VGAWing
 
 http://lucidscience.com/pro-vga%20video%20generator-2.aspx
+
+https://sites.google.com/site/h2obsession/CBM/C128/rgbi-to-vga
diff -r 27660220db5a -r 81ee57d5c082 tools/makeimage.py
--- a/tools/makeimage.py	Thu May 18 01:58:26 2017 +0200
+++ b/tools/makeimage.py	Thu May 18 23:50:22 2017 +0200
@@ -2,7 +2,7 @@
 
 """
 Convert images for display in an Acorn Electron MODE 2 variant with a pixel
-layout of R0RGGGBB, giving 128 colours instead of the usual 8 colours.
+layout of I0RRGGBB, giving 128 colours instead of the usual 8 colours.
 
 Copyright (C) 2015, 2017 Paul Boddie <paul@boddie.org.uk>
 
@@ -17,12 +17,6 @@
 
 You should have received a copy of the GNU General Public License along
 with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-----
-
-ImageMagick can be used to dither images to a 232 palette before conversion:
-
-convert in.png -ordered-dither threshold,4,8,4 out.png
 """
 
 from os.path import split, splitext
@@ -76,15 +70,19 @@
 
                     else:
                         r, g, b = data.next()
+                        rm, gm, bm, i = get_values(r, g, b)
+
+                        # Encode the byte value: I0RRGGBB.
+
                         word.insert(0,
-                            # R<7> -> D<7>
-                            (r & 0x80) |
-                            # R<6> -> D<5>
-                            ((r & 0x40) >> 1) |
-                            # G<7:5> -> D<4:2>
-                            ((g >> 5) << 2) |
+                            # I -> D<7>
+                            (i << 7) |
+                            # R<7:6> -> D<5:4>
+                            (rm >> 2) |
+                            # G<7:6> -> D<3:2>
+                            (gm >> 4) |
                             # B<7:6> -> D<1:0>
-                            (b >> 6))
+                            (bm >> 6))
 
                     flush_word(f, word)
                     x += 1
@@ -96,11 +94,28 @@
     finally:
         f.close()
 
+def get_values(r, g, b):
+
+    "Return modified values for 'r', 'g' and 'b', plus an intensity bit."
+
+    rm = r & 0xc0
+    gm = g & 0xc0
+    bm = b & 0xc0
+    rd = r - rm
+    gd = g - gm
+    bd = b - bm
+    i = ((rd ** 2 + gd ** 2 + bd ** 2) ** 0.5) >= 32 and 1 or 0
+    return rm, gm, bm, i
+
 def make_preview(im):
     imp = PIL.Image.new("RGB", im.size)
     data = []
     for r, g, b in im.getdata():
-        data.append((((r >> 6) << 6), ((g >> 5) << 5), (b >> 6) << 6))
+        rm, gm, bm, i = get_values(r, g, b)
+        r = rm + (i * 32)
+        g = gm + (i * 32)
+        b = bm + (i * 32)
+        data.append((r, g, b))
     imp.putdata(data)
     return imp