Revert "Fix C extension build warnings"

This reverts commit 03a8697866.

Turns out there was a good reason for this: it makes Overviewer work on
Debian. Why? Who knows. It's a mystery.

overviewer_core/src/Draw.c

@@ -64,6 +64,13 @@
 #define INK8(ink) (*(UINT8*)ink)
 #define INK32(ink) (*(INT32*)ink)
 
+/* like (a * b + 127) / 255), but much faster on most platforms */
+#define MULDIV255(a, b, tmp)\
+        (tmp = (a) * (b) + 128, ((((tmp) >> 8) + (tmp)) >> 8))
+
+#define BLEND(mask, in1, in2, tmp1, tmp2)\
+        (MULDIV255(in1, 255 - mask, tmp1) + MULDIV255(in2, mask, tmp2))
+
 /* -------------------------------------------------------------------- */
 /* Primitives                                                           */
 /* -------------------------------------------------------------------- */
@@ -93,14 +100,14 @@ point32(Imaging im, int x, int y, int ink)
 static inline void
 point32rgba(Imaging im, int x, int y, int ink)
 {
-    unsigned int tmp1;
+    unsigned int tmp1, tmp2;
 
     if (x >= 0 && x < im->xsize && y >= 0 && y < im->ysize) {
         UINT8* out = (UINT8*) im->image[y]+x*4;
         UINT8* in = (UINT8*) &ink;
-        out[0] = BLEND(in[3], out[0], in[0], tmp1);
+        out[0] = BLEND(in[3], out[0], in[0], tmp1, tmp2);
-        out[1] = BLEND(in[3], out[1], in[1], tmp1);
+        out[1] = BLEND(in[3], out[1], in[1], tmp1, tmp2);
-        out[2] = BLEND(in[3], out[2], in[2], tmp1);
+        out[2] = BLEND(in[3], out[2], in[2], tmp1, tmp2);
     }
 }
 
@@ -152,7 +159,7 @@ static inline void
 hline32rgba(Imaging im, int x0, int y0, int x1, int ink)
 {
     int tmp;
-    unsigned int tmp1;
+    unsigned int tmp1, tmp2;
 
     if (y0 >= 0 && y0 < im->ysize) {
         if (x0 > x1)
@@ -169,9 +176,9 @@ hline32rgba(Imaging im, int x0, int y0, int x1, int ink)
             UINT8* out = (UINT8*) im->image[y0]+x0*4;
             UINT8* in = (UINT8*) &ink;
             while (x0 <= x1) {
-                out[0] = BLEND(in[3], out[0], in[0], tmp1);
+                out[0] = BLEND(in[3], out[0], in[0], tmp1, tmp2);
-                out[1] = BLEND(in[3], out[1], in[1], tmp1);
+                out[1] = BLEND(in[3], out[1], in[1], tmp1, tmp2);
-                out[2] = BLEND(in[3], out[2], in[2], tmp1);
+                out[2] = BLEND(in[3], out[2], in[2], tmp1, tmp2);
                 x0++; out += 4;
             }
         }

overviewer_core/src/overviewer.h

@@ -33,7 +33,7 @@
 
 // increment this value if you've made a change to the c extesion
 // and want to force users to rebuild
-#define OVERVIEWER_EXTENSION_VERSION 55
+#define OVERVIEWER_EXTENSION_VERSION 54
 
 /* Python PIL, and numpy headers */
 #include <Python.h>
@@ -42,6 +42,11 @@
 /* Fix Pillow on mingw-w64 which includes windows.h in Imaging.h */
 #undef TRANSPARENT
 
+/* like (a * b + 127) / 255), but much faster on most platforms
+   from PIL's _imaging.c */
+#define MULDIV255(a, b, tmp)								\
+	(tmp = (a) * (b) + 128, ((((tmp) >> 8) + (tmp)) >> 8))
+
 /* macro for getting a value out of various numpy arrays the 3D arrays have
    interesting, swizzled coordinates because minecraft (anvil) stores blocks
    in y/z/x order for 3D, z/x order for 2D */