demux_mf: support .xbm

And support the PIX_FMT_MONOWHITE pixel format. (This is really weird:
unlike PIX_FMT_MONOBLACK, it uses white pixels. I have no idea why
libavcodec doesn't just convert the pixel format on the fly, instead of
bothering everyone with really special pixel formats.)

demux/demux_mf.c

@@ -127,6 +127,7 @@ static const struct {
   { "im8",  "sunrast" },
   { "im24",  "sunrast" },
   { "sunras",  "sunrast" },
+  { "xbm",  "xbm" },
   {0}
 };
 

video/filter/vf_scale.c

@@ -132,6 +132,7 @@ static const unsigned int outfmt_list[]={
     IMGFMT_RGB4_BYTE,
     IMGFMT_BGR4_BYTE,
     IMGFMT_MONO,
+    IMGFMT_MONO_W,
     0
 };
 

video/fmt-conversion.c

@@ -38,6 +38,7 @@ static const struct {
     {IMGFMT_BGR8,  PIX_FMT_RGB8},
     {IMGFMT_BGR4,  PIX_FMT_RGB4},
     {IMGFMT_MONO,  PIX_FMT_MONOBLACK},
+    {IMGFMT_MONO_W,  PIX_FMT_MONOWHITE},
     {IMGFMT_RGB4_BYTE,  PIX_FMT_BGR4_BYTE},
     {IMGFMT_BGR4_BYTE,  PIX_FMT_RGB4_BYTE},
     {IMGFMT_RGB48_LE, PIX_FMT_RGB48LE},

video/img_format.h

@@ -197,6 +197,7 @@ enum mp_imgfmt {
     IMGFMT_RGB4,                // r1 g2 b1, bit-packed
     IMGFMT_BGR4,
     IMGFMT_MONO,                // 1 bit per pixel, bit-packed
+    IMGFMT_MONO_W,              // like IMGFMT_MONO, but inverted (white pixels)
 
     // Accessed with bit-shifts after endian-swapping the uint16_t pixel
     IMGFMT_RGB12_LE,            // 4r 4g 4b 4a  (LSB to MSB)