UF16 is not FP16

radarhere · Jun 4, 2022 · 3b51e1c · 3b51e1c
1 parent b37f2d1
commit 3b51e1c
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Showing 3 changed files with 13 additions and 15 deletions.
diff --git a/src/PIL/DdsImagePlugin.py b/src/PIL/DdsImagePlugin.py
@@ -101,6 +101,7 @@
 DXGI_FORMAT_BC5_TYPELESS = 82
 DXGI_FORMAT_BC5_UNORM = 83
 DXGI_FORMAT_BC5_SNORM = 84
+DXGI_FORMAT_BC6H_UF16 = 95
 DXGI_FORMAT_BC7_TYPELESS = 97
 DXGI_FORMAT_BC7_UNORM = 98
 DXGI_FORMAT_BC7_UNORM_SRGB = 99
@@ -173,6 +174,10 @@ def _open(self):
                     self.pixel_format = "BC5S"
                     n = 5
                     self.mode = "RGB"
+                elif dxgi_format == DXGI_FORMAT_BC6H_UF16:
+                    self.pixel_format = "BC6"
+                    n = 6
+                    self.mode = "RGB"
                 elif dxgi_format in (DXGI_FORMAT_BC7_TYPELESS, DXGI_FORMAT_BC7_UNORM):
                     self.pixel_format = "BC7"
                     n = 7

diff --git a/src/decode.c b/src/decode.c
@@ -376,11 +376,8 @@ PyImaging_BcnDecoderNew(PyObject *self, PyObject *args) {
             actual = "L";
             break;
         case 5: /* BC5: 2-channel 8-bit via 2 BC3 alpha blocks */
-            actual = "RGB";
-            break;
         case 6: /* BC6: 3-channel 16-bit float */
-            /* TODO: support 4-channel floating point images */
-            actual = "RGBAF";
+            actual = "RGB";
             break;
         default:
             PyErr_SetString(PyExc_ValueError, "block compression type unknown");

diff --git a/src/libImaging/BcnDecode.c b/src/libImaging/BcnDecode.c
@@ -23,10 +23,6 @@ typedef struct {
     UINT8 l;
 } lum;
 
-typedef struct {
-    FLOAT32 r, g, b;
-} rgb32f;
-
 typedef struct {
     UINT16 c0, c1;
     UINT32 lut;
@@ -667,22 +663,22 @@ half_to_float(UINT16 h) {
     return o.f;
 }
 
-static float
+static UINT8
 bc6_finalize(int v, int sign) {
     if (sign) {
         if (v < 0) {
             v = ((-v) * 31) / 32;
-            return half_to_float((UINT16)(0x8000 | v));
+            return (UINT8)half_to_float((UINT16)(0x8000 | v));
         } else {
-            return half_to_float((UINT16)((v * 31) / 32));
+            return (UINT8)half_to_float((UINT16)((v * 31) / 32));
         }
     } else {
-        return half_to_float((UINT16)((v * 31) / 64));
+        return v >> 8;
     }
 }
 
 static void
-bc6_lerp(rgb32f *col, int *e0, int *e1, int s, int sign) {
+bc6_lerp(rgba *col, int *e0, int *e1, int s, int sign) {
     int r, g, b;
     int t = 64 - s;
     r = (e0[0] * t + e1[0] * s) >> 6;
@@ -694,7 +690,7 @@ bc6_lerp(rgb32f *col, int *e0, int *e1, int s, int sign) {
 }
 
 static void
-decode_bc6_block(rgb32f *col, const UINT8 *src, int sign) {
+decode_bc6_block(rgba *col, const UINT8 *src, int sign) {
     UINT16 endpoints[12]; /* storage for r0, g0, b0, r1, ... */
     int ueps[12];
     int i, i0, ib2, di, dw, mask, numep, s;
@@ -862,7 +858,7 @@ decode_bcn(
             break;
         case 6:
             while (bytes >= 16) {
-                rgb32f col[16];
+                rgba col[16];
                 decode_bc6_block(col, ptr, (state->state >> 4) & 1);
                 put_block(im, state, (const char *)col, sizeof(col[0]), C);
                 ptr += 16;