# HG changeset patch
# User Matti Hamalainen <ccr@tnsp.org>
# Date 1551791358 -7200
# Node ID 81fb21dd326547209831d6d3548245fea925ee0c
# Parent  dac89484f143c5295aa4e32f9c9cd3c023e93536
Add dmGetNPlanesFromNColors() and use it.

diff -r dac89484f143 -r 81fb21dd3265 tools/gfxconv.c
--- a/tools/gfxconv.c	Tue Mar 05 14:51:02 2019 +0200
+++ b/tools/gfxconv.c	Tue Mar 05 15:09:18 2019 +0200
@@ -1424,21 +1424,13 @@
 
     // Determine number of planes, if paletted
     if (spec->format == DM_COLFMT_PALETTE &&
-        spec->nplanes == 0)
-    {
-        for (int n = 8; n >= 0;)
-        {
-            if ((image->pal->ncolors - 1) & (1 << n))
-            {
-                spec->nplanes = n + 1;
-                break;
-            }
-            else
-                n--;
-        }
-    }
+        spec->nplanes == 0 && image->pal != NULL)
+        spec->nplanes = dmGetNPlanesFromNColors(image->pal->ncolors);
+    else
+    if (image->format == DM_COLFMT_GRAYSCALE)
+        spec->nplanes = 8;
 
-    if (spec->nplanes == 0)
+    if (spec->nplanes <= 0)
         spec->nplanes = 4;
 
     spec->fmtid = fmt->fmtid;
diff -r dac89484f143 -r 81fb21dd3265 tools/libgfx.c
--- a/tools/libgfx.c	Tue Mar 05 14:51:02 2019 +0200
+++ b/tools/libgfx.c	Tue Mar 05 15:09:18 2019 +0200
@@ -91,6 +91,23 @@
 }
 
 
+int dmGetNPlanesFromNColors(const int ncolors)
+{
+    if (ncolors <= 0)
+        return -1;
+
+    for (int n = 8; n >= 0;)
+    {
+        if ((ncolors - 1) & (1 << n))
+            return n + 1;
+        else
+            n--;
+    }
+
+    return -2;
+}
+
+
 BOOL dmCompareColor(const DMColor *c1, const DMColor *c2, const BOOL alpha)
 {
     if (c1->r == c2->r &&
diff -r dac89484f143 -r 81fb21dd3265 tools/libgfx.h
--- a/tools/libgfx.h	Tue Mar 05 14:51:02 2019 +0200
+++ b/tools/libgfx.h	Tue Mar 05 15:09:18 2019 +0200
@@ -132,6 +132,7 @@
 int       dmImageGetBytesPerPixel(const int format);
 int       dmImageGetBitsPerPixel(const int format);
 int       dmImageProbeGeneric(const Uint8 *buf, const size_t len, const DMImageFormat **fmt, int *index);
+int       dmGetNPlanesFromNColors(const int ncolors);
 
 BOOL dmCompareColor(const DMColor *c1, const DMColor *c2, const BOOL alpha);
 int  dmPaletteAlloc(DMPalette **ppal, const int ncolors, const int ctransp);