dds: Add support for monochrome images

libavcodec/dds.c

@@ -240,6 +240,10 @@ static int parse_pixel_format(AVCodecContext *avctx)
             ctx->paletted   = 1;
             avctx->pix_fmt  = AV_PIX_FMT_PAL8;
             break;
+        case MKTAG('G', '1', ' ', ' '):
+            ctx->compressed = 0;
+            avctx->pix_fmt  = AV_PIX_FMT_MONOBLACK;
+            break;
         case MKTAG('D', 'X', '1', '0'):
             /* DirectX 10 extra header */
             dxgi = bytestream2_get_le32(gbc);

tests/fate/image.mak

@@ -65,6 +65,7 @@ DDS_FMT          = alpha8                                               \
                    dxt5-xrbg                                            \
                    dxt5-ycocg                                           \
                    dxt5-ycocg-scaled                                    \
+                   monob                                                \
                    pal                                                  \
                    pal-ati                                              \
                    rgb1555                                              \

tests/ref/fate/dds-monob

+#tb 0: 1/25
+0,          0,          0,        1,     1952, 0x716498a1