[PATCH libdrm v2 07/10] util: Add SMPTE pattern support for C1 format

[Geert Uytterhoeven <geert@linux-m68k.org>]

Add support for drawing the SMPTE pattern in a buffer using the C1
indexed format.

As only two colors are available, the pattern is drawn in black and
white, using Floyd-Steinberg dithering.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
v2:
  New.
---
 tests/util/pattern.c | 171 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 167 insertions(+), 4 deletions(-)

diff --git a/tests/util/pattern.c b/tests/util/pattern.c
index 8ed5f8dd1a6282f9..5ec7d66495209df4 100644
--- a/tests/util/pattern.c
+++ b/tests/util/pattern.c
@@ -668,6 +668,163 @@ static unsigned int smpte_bottom[8] = {
 	SMPTE_COLOR_BLACK,
 };
 
+/*
+ * Floyd-Steinberg dithering
+ */
+
+struct fsd {
+	unsigned int width;
+	unsigned int x;
+	unsigned int i;
+	int red;
+	int green;
+	int blue;
+	int error[];
+};
+
+static struct fsd *fsd_alloc(unsigned int width)
+{
+	unsigned int n = 3 * (width + 1);
+	struct fsd *fsd = malloc(sizeof(*fsd) + n * sizeof(fsd->error[0]));
+
+	fsd->width = width;
+	fsd->x = 0;
+	fsd->i = 0;
+	memset(fsd->error, 0, n * sizeof(fsd->error[0]));
+
+	return fsd;
+}
+
+static inline int clamp(int val, int min, int max)
+{
+	if (val < min)
+		return min;
+	if (val > max)
+		return max;
+	return val;
+}
+
+static void fsd_dither(struct fsd *fsd, struct drm_color_lut *color)
+{
+	unsigned int i = fsd->i;
+
+	fsd->red = (int)color->red + (fsd->error[3 * i] + 8) / 16;
+	fsd->green = (int)color->green + (fsd->error[3 * i + 1] + 8) / 16;
+	fsd->blue = (int)color->blue + (fsd->error[3 * i + 2] + 8) / 16;
+
+	color->red = clamp(fsd->red, 0, 65535);
+	color->green = clamp(fsd->green, 0, 65535);
+	color->blue = clamp(fsd->blue, 0, 65535);
+}
+
+static void fsd_update(struct fsd *fsd, const struct drm_color_lut *actual)
+{
+	int error_red = fsd->red - (int)actual->red;
+	int error_green = fsd->green - (int)actual->green;
+	int error_blue = fsd->blue - (int)actual->blue;
+	unsigned int width = fsd->width;
+	unsigned int i = fsd->i, j;
+	unsigned int n = width + 1;
+
+	/* Distribute errors over neighboring pixels */
+	if (fsd->x == width - 1) {
+		/* Last pixel on this scanline */
+		/* South East: initialize to zero */
+		fsd->error[3 * i] = 0;
+		fsd->error[3 * i + 1] = 0;
+		fsd->error[3 * i + 2] = 0;
+	} else {
+		/* East: accumulate error */
+		j = (i + 1) % n;
+		fsd->error[3 * j] += 7 * error_red;
+		fsd->error[3 * j + 1] += 7 * error_green;
+		fsd->error[3 * j + 2] += 7 * error_blue;
+
+		/* South East: initial error */
+		fsd->error[3 * i] = error_red;
+		fsd->error[3 * i + 1] = error_green;
+		fsd->error[3 * i + 2] = error_blue;
+	}
+	/* South West: accumulate error */
+	j = (i + width - 1) % n;
+	fsd->error[3 * j] += 3 * error_red;
+	fsd->error[3 * j + 1] += 3 * error_green;
+	fsd->error[3 * j + 2] += 3 * error_blue;
+
+	/* South: accumulate error */
+	j = (i + width) % n;
+	fsd->error[3 * j] += 5 * error_red;
+	fsd->error[3 * j + 1] += 5 * error_green;
+	fsd->error[3 * j + 2] += 5 * error_blue;
+
+	fsd->x = (fsd->x + 1) % width;
+	fsd->i = (fsd->i + 1) % n;
+}
+
+static void write_pixel_1(uint8_t *mem, unsigned int x, unsigned int pixel)
+{
+	unsigned int shift = 7 - (x & 7);
+	unsigned int mask = 1U << shift;
+
+	mem[x / 8] = (mem[x / 8] & ~mask) | ((pixel << shift) & mask);
+}
+
+static void write_color_1(struct fsd *fsd, uint8_t *mem, unsigned int x,
+			  unsigned int index)
+{
+	struct drm_color_lut color = smpte_color_lut[index];
+	unsigned int pixel;
+
+	fsd_dither(fsd, &color);
+
+	/* ITU BT.601: Y = 0.299 R + 0.587 G + 0.114 B */
+	if (3 * color.red + 6 * color.green + color.blue >= 10 * 32768) {
+		pixel = 1;
+		color.red = color.green = color.blue = 65535;
+	} else {
+		pixel = 0;
+		color.red = color.green = color.blue = 0;
+	}
+
+	fsd_update(fsd, &color);
+
+	write_pixel_1(mem, x, pixel);
+}
+
+static void fill_smpte_c1(void *mem, unsigned int width, unsigned int height,
+			  unsigned int stride)
+{
+	struct fsd *fsd = fsd_alloc(width);
+	unsigned int x;
+	unsigned int y;
+
+	for (y = 0; y < height * 6 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_color_1(fsd, mem, x, smpte_top[x * 7 / width]);
+		mem += stride;
+	}
+
+	for (; y < height * 7 / 9; ++y) {
+		for (x = 0; x < width; ++x)
+			write_color_1(fsd, mem, x, smpte_middle[x * 7 / width]);
+		mem += stride;
+	}
+
+	for (; y < height; ++y) {
+		for (x = 0; x < width * 5 / 7; ++x)
+			write_color_1(fsd, mem, x,
+				      smpte_bottom[x * 4 / (width * 5 / 7)]);
+		for (; x < width * 6 / 7; ++x)
+			write_color_1(fsd, mem, x,
+				      smpte_bottom[(x - width * 5 / 7) * 3 /
+						   (width / 7) + 4]);
+		for (; x < width; ++x)
+			write_color_1(fsd, mem, x, smpte_bottom[7]);
+		mem += stride;
+	}
+
+	free(fsd);
+}
 static void write_pixel_4(uint8_t *mem, unsigned int x, unsigned int pixel)
 {
 	if (x & 1)
@@ -742,9 +899,8 @@ static void fill_smpte_c8(void *mem, unsigned int width, unsigned int height,
 
 void util_smpte_index_gamma(unsigned size, struct drm_color_lut *lut)
 {
-	if (size < ARRAY_SIZE(smpte_color_lut)) {
-		printf("Error: gamma too small: %u < %zu\n", size,
-		       ARRAY_SIZE(smpte_color_lut));
+	if (size < 2) {
+		printf("Error: gamma too small: %u < 2\n", size);
 		return;
 	}
 	memset(lut, 0, size * sizeof(struct drm_color_lut));
@@ -754,7 +910,12 @@ void util_smpte_index_gamma(unsigned size, struct drm_color_lut *lut)
 	lut[idx].green = (g) * 0x101; \
 	lut[idx].blue = (b) * 0x101
 
-	memcpy(lut, smpte_color_lut, sizeof(smpte_color_lut));
+	if (size < ARRAY_SIZE(smpte_color_lut)) {
+		FILL_COLOR(0, 0,   0,   0  );	/* black */
+		FILL_COLOR(1, 255, 255, 255);	/* white */
+	} else {
+		memcpy(lut, smpte_color_lut, sizeof(smpte_color_lut));
+	}
 
 #undef FILL_COLOR
 }
@@ -766,6 +927,8 @@ static void fill_smpte(const struct util_format_info *info, void *planes[3],
 	unsigned char *u, *v;
 
 	switch (info->format) {
+	case DRM_FORMAT_C1:
+		return fill_smpte_c1(planes[0], width, height, stride);
 	case DRM_FORMAT_C4:
 		return fill_smpte_c4(planes[0], width, height, stride);
 	case DRM_FORMAT_C8:
-- 
2.25.1