From: Niklas Söderlund <[email protected]> The HGT can operate with hue areas which are not directly adjoined. In this mode of operation hue values which are between two areas are attributed to both areas with a weight for the final histogram.
Add support to generate such histograms using gen-image which can be used to verify correct operation of the HGT. Previously gen-image could only generate histograms with adjoined areas. Signed-off-by: Niklas Söderlund <[email protected]> --- src/gen-image.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 79 insertions(+), 19 deletions(-) diff --git a/src/gen-image.c b/src/gen-image.c index 688f602..9cd5eb9 100644 --- a/src/gen-image.c +++ b/src/gen-image.c @@ -1301,7 +1301,7 @@ static void histogram_compute_hgt(const struct image *image, void *histo, uint8_t rgb[3], hsv[3], smin = 255, smax = 0; uint32_t sum = 0, hist[6][32]; unsigned int x, y, i; - int m, n; + unsigned int hist_n, hue_pos; memset(hist, 0x00, sizeof(hist)); @@ -1317,24 +1317,84 @@ static void histogram_compute_hgt(const struct image *image, void *histo, smax = max(smax, hsv[1]); sum += hsv[1]; - /* Find m and n for hist */ - m = n = -1; - for (i = 0; i < 6 && m == -1; i++) - if (hsv[0] >= hue_areas[i*2] && (hsv[0] <= hue_areas[i*2+1])) - m = i; - for (i = 0; i < 32 && n == -1; i++) - if ((hsv[1] >= 8*i) && (hsv[1] < 8 * (i+1))) - n = i; + /* Find n for hist */ + hist_n = hsv[1] / 8; /* - * The HW supports a declining weight to be applied - * when hue areas are not directly adjoined. This - * test can not replicated this, the hue areas need - * to be set without any gaps else the weights from HW - * will be wrong. Max weight is 16. + * Find position in hue areas which is greater than the + * current H value. Special consideration is needed for: + * + * - Values inside a hue area are inclusive, values that + * are between two hue areas are exclusive. + * - Hue area 0 can wrap around the H value space, for + * example include values greater then 240 but less + * then 30. */ - if (m != -1 && n != -1) - hist[m][n] += 16; + for (i = 0; i < 12; i++) { + + /* Special cases when area 0 wraps around */ + if (hue_areas[0] > hue_areas[1]) { + + /* Check if pixel is inside the wrapped area 0 */ + if (hsv[0] > hue_areas[0] || hsv[0] <= hue_areas[1]) { + hue_pos = 1; + break; + } + + /* Exclude first area point from normal logic */ + if (!i) + continue; + } + + /* Check if H is inside one of the hue areas */ + if ((hsv[0] < hue_areas[i]) || (i % 2 && hsv[0] == hue_areas[i])) { + hue_pos = i; + break; + } + + /* Check if H is larger then area 5 */ + if (hsv[0] > hue_areas[11]) { + hue_pos = 0; + break; + } + } + + /* + * Figure out which areas the current H value should be + * attributed to. If the H value is inside one of the + * areas the max weight (16) is attributed to it else + * the weight is split between them based on how close + * the H value is to each area. + * + * If ''hue_pos'' are odd the H value is inside an area and + * it should be attributed the full weight to area hue_pos/2 + * else it should be split between area hue_pos/2 and + * hue_pos/2 - 1. + */ + if (hue_pos % 2) { + hist[hue_pos/2][hist_n] += 16; + } else { + unsigned int hue1, hue2; + unsigned int length, width, weight; + + hue1 = hue_areas[hue_pos ? hue_pos - 1 : 11]; + hue2 = hue_areas[hue_pos]; + + /* Calculate the total width between the two areas */ + width = hue2 - hue1 + (hue1 > hue2 ? 256 : 0); + + /* Calculate the length to the right most area */ + if (hue1 > hue2 && hsv[0] > hue1) + length = width - (hsv[0] - hue1); + else + length = abs(hsv[0] - hue2); + + /* Calculate weight and round up */ + weight = (length * 16 + width - 1) / width; + /* Split weight between the two areas */ + hist[hue_pos ? hue_pos/2 - 1 : 5][hist_n] += weight; + hist[hue_pos/2][hist_n] += 16 - weight; + } } } @@ -1349,9 +1409,9 @@ static void histogram_compute_hgt(const struct image *image, void *histo, histo += 4; /* Weighted Frequency of Hue Area-m and Saturation Area-n */ - for (m = 0; m < 6; m++) { - for (n = 0; n < 32; n++) { - *(uint32_t *)histo = hist[m][n]; + for (x = 0; x < 6; x++) { + for (y = 0; y < 32; y++) { + *(uint32_t *)histo = hist[x][y]; histo += 4; } } -- 2.9.3
