[PATCH libdrm v3 7/9] util: Add SMPTE pattern support for C2 format

[Geert Uytterhoeven]

Add support for drawing the SMPTE pattern in a buffer using the C2
indexed format.

As only four colors are available, resolution is halved, and the pattern
is drawn in a PenTile RG-GB matrix, using Floyd-Steinberg dithering.
The magnitude of the green subpixels is reduced, as there are twice as
many green subpixels as red or blue subpixels.

Signed-off-by: Geert Uytterhoeven <geert at linux-m68k.org>
Acked-by: Sam Ravnborg <sam at ravnborg.org>
---
Dithering example at https://drive.google.com/file/d/1g5O8XeacrjrC8rgaVENvR65YeI6QvmtO/view

v3:
  - Add Acked-by,

v2:
  - New.
---
 tests/util/pattern.c | 97 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 96 insertions(+), 1 deletion(-)

diff --git a/tests/util/pattern.c b/tests/util/pattern.c
index b85a1f4728b8be1c..1c6176b41506fa7d 100644
--- a/tests/util/pattern.c
+++ b/tests/util/pattern.c
@@ -825,6 +825,93 @@ static void fill_smpte_c1(void *mem, unsigned int width, unsigned int height,
 
 	free(fsd);
 }
+
+static void write_pixel_2(uint8_t *mem, unsigned int x, unsigned int pixel)
+{
+	unsigned int shift = 6 - 2 * (x & 3);
+	unsigned int mask = 3U << shift;
+
+	mem[x / 4] = (mem[x / 4] & ~mask) | ((pixel << shift) & mask);
+}
+
+static void write_color_2(struct fsd *fsd, uint8_t *mem, unsigned int stride,
+			  unsigned int x, unsigned int index)
+{
+	struct drm_color_lut color = smpte_color_lut[index];
+	unsigned int r, g, b;
+
+	fsd_dither(fsd, &color);
+
+	if (color.red >= 32768) {
+		r = 1;
+		color.red = 65535;
+	} else {
+		r = 0;
+		color.red = 0;
+	}
+	if (color.green >= 32768) {
+		g = 2;
+		color.green = 65535;
+	} else {
+		g = 0;
+		color.green = 0;
+	}
+	if (color.blue >= 32768) {
+		b = 3;
+		color.blue = 65535;
+	} else {
+		b = 0;
+		color.blue = 0;
+	}
+
+	fsd_update(fsd, &color);
+
+	/* Use PenTile RG-GB */
+	write_pixel_2(mem, 2 * x, r);
+	write_pixel_2(mem, 2 * x + 1, g);
+	write_pixel_2(mem + stride, 2 * x, g);
+	write_pixel_2(mem + stride, 2 * x + 1, b);
+}
+
+static void fill_smpte_c2(void *mem, unsigned int width, unsigned int height,
+			  unsigned int stride)
+{
+	struct fsd *fsd = fsd_alloc(width);
+	unsigned int x;
+	unsigned int y;
+
+	/* Half resolution for PenTile RG-GB */
+	width /= 2;
+	height /= 2;
+
+	for (y = 0; y < height * 6 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_color_2(fsd, mem, stride, x, smpte_top[x * 7 / width]);
+		mem += 2 * stride;
+	}
+
+	for (; y < height * 7 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_color_2(fsd, mem, stride, x, smpte_middle[x * 7 / width]);
+		mem += 2 * stride;
+	}
+
+	for (; y < height; ++y) {
+		for (x = 0; x < width * 5 / 7; ++x)
+			write_color_2(fsd, mem, stride, x,
+				      smpte_bottom[x * 4 / (width * 5 / 7)]);
+		for (; x < width * 6 / 7; ++x)
+			write_color_2(fsd, mem, stride, x,
+				      smpte_bottom[(x - width * 5 / 7) * 3 /
+						   (width / 7) + 4]);
+		for (; x < width; ++x)
+			write_color_2(fsd, mem, stride, x, smpte_bottom[7]);
+		mem += 2 * stride;
+	}
+
+	free(fsd);
+}
+
 static void write_pixel_4(uint8_t *mem, unsigned int x, unsigned int pixel)
 {
 	if (x & 1)
@@ -910,9 +997,15 @@ void util_smpte_index_gamma(unsigned size, struct drm_color_lut *lut)
 	lut[idx].green = (g) * 0x101; \
 	lut[idx].blue = (b) * 0x101
 
-	if (size < ARRAY_SIZE(smpte_color_lut)) {
+	if (size < 4) {
 		FILL_COLOR(0, 0,   0,   0  );	/* black */
 		FILL_COLOR(1, 255, 255, 255);	/* white */
+	} else if (size < ARRAY_SIZE(smpte_color_lut)) {
+		/* PenTile RG-GB */
+		FILL_COLOR(0, 0,   0,   0  );	/* black */
+		FILL_COLOR(1, 255, 0,   0  );	/* red */
+		FILL_COLOR(2, 0,   207, 0  );	/* green */
+		FILL_COLOR(3, 0,   0,   255);	/* blue */
 	} else {
 		memcpy(lut, smpte_color_lut, sizeof(smpte_color_lut));
 	}
@@ -929,6 +1022,8 @@ static void fill_smpte(const struct util_format_info *info, void *planes[3],
 	switch (info->format) {
 	case DRM_FORMAT_C1:
 		return fill_smpte_c1(planes[0], width, height, stride);
+	case DRM_FORMAT_C2:
+		return fill_smpte_c2(planes[0], width, height, stride);
 	case DRM_FORMAT_C4:
 		return fill_smpte_c4(planes[0], width, height, stride);
 	case DRM_FORMAT_C8:
-- 
2.34.1