util: add SMPTE pattern support for C1 format

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[1].

[1] https://en.wikipedia.org/wiki/Floyd%E2%80%93Steinberg_dithering

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
Dithering example at https://drive.google.com/file/d/1waJczErrIaEKRhBCCU1ynxRG8agpo0Xx/view

v5:
  - Add Reviewed-by,

v4:
  - Replace FILL_COLOR() use by bw_color_lut[],

v3:
  - Add Acked-by,
  - Add Wikipedia link,

v2:
  New.

diff --git a/tests/util/pattern.c b/tests/util/pattern.c
index 1707426..2362555 100644 (file)
--- a/tests/util/pattern.c
+++ b/tests/util/pattern.c
@@ -654,6 +654,11 @@ static unsigned int smpte_bottom[8] = {
 
 #define EXPAND_COLOR(r, g, b)  { (r) * 0x101, (g) * 0x101, (b) * 0x101 }
 
+static const struct drm_color_lut bw_color_lut[] = {
+       EXPAND_COLOR(  0,   0,   0),    /* black */
+       EXPAND_COLOR(255, 255, 255),    /* white */
+};
+
 static const struct drm_color_lut smpte_color_lut[] = {
        [SMPTE_COLOR_GREY] =        EXPAND_COLOR(192, 192, 192),
        [SMPTE_COLOR_YELLOW] =      EXPAND_COLOR(192, 192,   0),
@@ -672,6 +677,164 @@ static const struct drm_color_lut smpte_color_lut[] = {
 
 #undef EXPAND_COLOR
 
+/*
+ * 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)
@@ -746,14 +909,17 @@ static void fill_smpte_c8(void *mem, unsigned int width, unsigned int height,
 
 void util_smpte_fill_lut(unsigned int ncolors, struct drm_color_lut *lut)
 {
-       if (ncolors < ARRAY_SIZE(smpte_color_lut)) {
+       if (ncolors < ARRAY_SIZE(bw_color_lut)) {
                printf("Error: lut too small: %u < %zu\n", ncolors,
-                      ARRAY_SIZE(smpte_color_lut));
+                      ARRAY_SIZE(bw_color_lut));
                return;
        }
        memset(lut, 0, ncolors * sizeof(struct drm_color_lut));
 
-       memcpy(lut, smpte_color_lut, sizeof(smpte_color_lut));
+       if (ncolors < ARRAY_SIZE(smpte_color_lut))
+               memcpy(lut, bw_color_lut, sizeof(bw_color_lut));
+       else
+               memcpy(lut, smpte_color_lut, sizeof(smpte_color_lut));
 }
 
 static void fill_smpte(const struct util_format_info *info, void *planes[3],
@@ -763,6 +929,8 @@ 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: