a/util + xrt: Add BC4 image support

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2457>

src/xrt/auxiliary/util/CMakeLists.txt

@@ -117,6 +117,7 @@ target_link_libraries(
 	aux_util
 	PUBLIC
 		xrt-external-nanopb
+		xrt-external-bcdec
 		aux-includes
 		aux_generated_bindings
 		aux_os

src/xrt/auxiliary/util/u_format.c

@@ -29,6 +29,7 @@ u_format_str(enum xrt_format f)
 	case XRT_FORMAT_YUYV422: return "XRT_FORMAT_YUYV422";
 	case XRT_FORMAT_UYVY422: return "XRT_FORMAT_UYVY422";
 	case XRT_FORMAT_MJPEG: return "XRT_FORMAT_MJPEG";
+	case XRT_FORMAT_BC4: return "XRT_FORMAT_BC4";
 	default: assert(!"unsupported format"); return 0;
 	}
 }
@@ -49,6 +50,7 @@ u_format_is_blocks(enum xrt_format f)
 	case XRT_FORMAT_YUV888:
 	case XRT_FORMAT_YUYV422:
 	case XRT_FORMAT_UYVY422:
+	case XRT_FORMAT_BC4:
 		// Yes
 		return true;
 	case XRT_FORMAT_MJPEG:
@@ -80,6 +82,9 @@ u_format_block_width(enum xrt_format f)
 	case XRT_FORMAT_BITMAP_8X1:
 		// Eight pixels per block.
 		return 8; // NOLINT
+	case XRT_FORMAT_BC4:
+		// four pixels wide
+		return 4;
 	default: assert(!"unsupported format"); return 0;
 	}
 }
@@ -104,6 +109,9 @@ u_format_block_height(enum xrt_format f)
 	case XRT_FORMAT_BITMAP_8X8:
 		// Eight pixels high.
 		return 8;
+	case XRT_FORMAT_BC4:
+		// four pixels high
+		return 4;
 	default: assert(!"unsupported format"); return 0;
 	}
 }
@@ -131,8 +139,8 @@ u_format_block_size(enum xrt_format f)
 	case XRT_FORMAT_UYVY422: // Four bytes per two pixels.
 		// 32bit pixel formats.
 		return 4;
-	case XRT_FORMAT_BITMAP_8X8: // 64 bits.
-		return 8;
+	case XRT_FORMAT_BC4: // 64 bits.
+	case XRT_FORMAT_BITMAP_8X8: return 8;
 	default: assert(!"unsupported format"); return 0;
 	}
 }

src/xrt/auxiliary/util/u_sink_converter.c

@@ -22,6 +22,9 @@
 #include "jpeglib.h"
 #endif
 
+#define BCDEC_IMPLEMENTATION
+#define BCDEC_BC4BC5_PRECISE
+#include "bcdec.h"
 
 /*
  *
@@ -390,6 +393,29 @@ from_MJPEG_to_YUV888(struct xrt_frame *dst_frame, size_t size, const uint8_t *da
 }
 #endif
 
+/*
+ *
+ * BC4
+ *
+ */
+
+static void
+from_BC4_to_L8(struct xrt_frame *dst_frame, uint32_t w, uint32_t h, size_t stride, const uint8_t *data)
+{
+	SINK_TRACE_MARKER();
+
+	assert(w % 4 == 0);
+	assert(h % 4 == 0);
+
+	const uint8_t *src = data;
+	for (uint32_t y = 0; y < h; y += 4) {
+		for (uint32_t x = 0; x < w; x += 4) {
+			bcdec_bc4(src, dst_frame->data + (y * dst_frame->stride) + x, dst_frame->stride, false);
+
+			src += BCDEC_BC4_BLOCK_SIZE;
+		}
+	}
+}
 
 /*
  *
@@ -485,6 +511,12 @@ convert_frame_l8(struct xrt_frame_sink *xs, struct xrt_frame *xf)
 	struct xrt_frame *converted = NULL;
 
 	switch (xf->format) {
+	case XRT_FORMAT_BC4:
+		if (!create_frame_with_format(xf, XRT_FORMAT_L8, &converted)) {
+			return;
+		}
+		from_BC4_to_L8(converted, xf->width, xf->height, xf->stride, xf->data);
+		break;
 	case XRT_FORMAT_L8: s->downstream->push_frame(s->downstream, xf); return;
 	case XRT_FORMAT_YUYV422:
 		if (!create_frame_with_format(xf, XRT_FORMAT_L8, &converted)) {
@@ -521,6 +553,12 @@ convert_frame_r8g8b8_or_l8(struct xrt_frame_sink *xs, struct xrt_frame *xf)
 		}
 		from_BAYER_GR8_to_R8G8B8(converted, w, h, xf->stride, xf->data);
 		break;
+	case XRT_FORMAT_BC4:
+		if (!create_frame_with_format(xf, XRT_FORMAT_L8, &converted)) {
+			return;
+		}
+		from_BC4_to_L8(converted, xf->width, xf->height, xf->stride, xf->data);
+		break;
 	case XRT_FORMAT_YUYV422:
 		if (!create_frame_with_format(xf, XRT_FORMAT_R8G8B8, &converted)) {
 			return;

src/xrt/include/xrt/xrt_defines.h

@@ -192,6 +192,8 @@ enum xrt_format
 	XRT_FORMAT_UYVY422,
 
 	XRT_FORMAT_MJPEG,
+
+	XRT_FORMAT_BC4,
 };
 
 /*!