color: run vec3 through weston_color_curve_sample()

Future development will need to evaluate pipelines with curves and
matrices. Such pipelines naturally operate on vec3, as matrices cannot
be operated one channel at a time. Make weston_color_curve_sample()
operate on arrays of vec3.

Its currently only caller, weston_color_curve_to_3x1D_LUT(), is modified
to employ a temporary array for the API impedance mismatch. This
workaround will be removed later as weston_color_curve_to_3x1D_LUT()
itself will be converted to operate on vec3 arrays.

weston_v3f_array_to_planar() documentation was generated with AI.

weston_color_curve_sample() is restructured a little bit, attempting to
make it simpler to read.

color-operations.h gets the #includes needed to make it self-standing.

Assisted-by: Github Copilot (Claude Sonnet 3.5)
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

include/libweston/linalg-3.h

@@ -30,6 +30,7 @@ extern "C" {
 #endif
 
 #include <stdbool.h>
+#include <stddef.h>
 #include <math.h>
 
 #include <libweston/linalg-types.h>
@@ -95,6 +96,37 @@ weston_v3f_dot_v3f(struct weston_vec3f a, struct weston_vec3f b)
 	return a.x * b.x + a.y * b.y + a.z * b.z;
 }
 
+/**
+ * Convert an array of vec3f into planar format
+ *
+ * Takes an array of RGB triplets and converts it into a planar format where all R
+ * values come first, then all G values, then all B values.
+ *
+ * \param planar The destination array for planar data, must have space for 3 * len floats
+ * \param arr Array of RGB triplets as vec3f structs
+ * \param len Number of RGB triplets in the array
+ */
+static inline void
+weston_v3f_array_to_planar(float *planar, const struct weston_vec3f *arr, size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i++) {
+		planar[i          ] = arr[i].r;
+		planar[i +     len] = arr[i].g;
+		planar[i + 2 * len] = arr[i].b;
+	}
+}
+
+/** Clamp each element to the range [a, b], replacing NaN with a. */
+static inline struct weston_vec3f
+weston_v3f_clamp(struct weston_vec3f v, float a, float b)
+{
+	return WESTON_VEC3F(v.x >= a ? (v.x <= b ? v.x : b) : a,
+			    v.y >= a ? (v.y <= b ? v.y : b) : a,
+			    v.z >= a ? (v.z <= b ? v.z : b) : a);
+}
+
 /**
  * Matrix infinity-norm
  *

libweston/color-operations.c

@@ -32,21 +32,6 @@
 #include "shared/helpers.h"
 #include "shared/weston-assert.h"
 
-/**
- * Clamp value to [0.0, 1.0], except pass NaN through.
- *
- * This function is not intended for hiding NaN.
- */
-static float
-ensure_unorm(float v)
-{
-	if (v <= 0.0f)
-		return 0.0f;
-	if (v > 1.0f)
-		return 1.0f;
-	return v;
-}
-
 static float
 linpow(float x, const union weston_color_curve_parametric_chan_data *p)
 {
@@ -61,18 +46,21 @@ linpow(float x, const union weston_color_curve_parametric_chan_data *p)
 }
 
 static void
-sample_linpow(const union weston_color_curve_parametric_chan_data *p,
-	      uint32_t len, bool clamp_input, float *in, float *out)
+sample_linpow(const union weston_color_curve_parametric_data *p,
+	      bool clamp_input, const struct weston_vec3f *in,
+	      struct weston_vec3f *out, size_t len)
 {
-	float x;
-	unsigned int i;
+	struct weston_vec3f tmp;
+	size_t i;
 
 	for (i = 0; i < len; i++) {
-		x = in[i];
+		tmp = in[i];
 		if (clamp_input)
-			x = ensure_unorm(x);
+			tmp = weston_v3f_clamp(tmp, 0.0f, 1.0f);
 
-		out[i] = linpow(x, p);
+		out[i] = WESTON_VEC3F(linpow(tmp.x, &p->chan[0]),
+				      linpow(tmp.y, &p->chan[1]),
+				      linpow(tmp.z, &p->chan[2]));
 	}
 }
 
@@ -90,21 +78,43 @@ powlin(float x, const union weston_color_curve_parametric_chan_data *p)
 }
 
 static void
-sample_powlin(const union weston_color_curve_parametric_chan_data *p,
-	      uint32_t len, bool clamp_input, float *in, float *out)
+sample_powlin(const union weston_color_curve_parametric_data *p,
+	      bool clamp_input, const struct weston_vec3f *in,
+	      struct weston_vec3f *out, size_t len)
 {
-	float x;
-	unsigned int i;
+	struct weston_vec3f tmp;
+	size_t i;
 
 	for (i = 0; i < len; i++) {
-		x = in[i];
+		tmp = in[i];
 		if (clamp_input)
-			x = ensure_unorm(x);
+			tmp = weston_v3f_clamp(tmp, 0.0f, 1.0f);
 
-		out[i] = powlin(x, p);
+		out[i] = WESTON_VEC3F(powlin(tmp.x, &p->chan[0]),
+				      powlin(tmp.y, &p->chan[1]),
+				      powlin(tmp.z, &p->chan[2]));
 	}
 }
 
+static void
+sample_parametric(struct weston_compositor *compositor,
+		  const struct weston_color_curve_parametric *param,
+		  const struct weston_vec3f *in,
+		  struct weston_vec3f *out,
+		  size_t len)
+{
+	switch (param->type) {
+	case WESTON_COLOR_CURVE_PARAMETRIC_TYPE_LINPOW:
+		sample_linpow(&param->params, param->clamped_input, in, out, len);
+		return;
+	case WESTON_COLOR_CURVE_PARAMETRIC_TYPE_POWLIN:
+		sample_powlin(&param->params, param->clamped_input, in, out, len);
+		return;
+	}
+
+	weston_assert_not_reached(compositor, "unknown parametric color curve");
+}
+
 static float
 perceptual_quantizer(float x)
 {
@@ -142,44 +152,52 @@ perceptual_quantizer_inverse(float x)
 }
 
 static void
-sample_pq(enum weston_tf_direction tf_direction, uint32_t ch, uint32_t len,
-	  float *in, float *out)
+sample_pq(enum weston_tf_direction tf_direction,
+	  const struct weston_vec3f *in,
+	  struct weston_vec3f *out,
+	  size_t len)
 {
-	unsigned int i;
-	float x;
+	struct weston_vec3f tmp;
+	size_t i;
 
-	for (i = 0; i < len; i++) {
-		/**
-		 * PQ and inverse PQ are always clamped, undefined for values
-		 * out of [0, 1] range.
-		 */
-		x = ensure_unorm(in[i]);
-
-		if (tf_direction == WESTON_FORWARD_TF)
-			out[i] = perceptual_quantizer(x);
-		else
-			out[i] = perceptual_quantizer_inverse(x);
+	switch (tf_direction) {
+	case WESTON_FORWARD_TF:
+		for (i = 0; i < len; i++) {
+			tmp = weston_v3f_clamp(in[i], 0.0f, 1.0f);
+			out[i] = WESTON_VEC3F(perceptual_quantizer(tmp.x),
+					      perceptual_quantizer(tmp.y),
+					      perceptual_quantizer(tmp.z));
+		}
+		break;
+	case WESTON_INVERSE_TF:
+		for (i = 0; i < len; i++) {
+			tmp = weston_v3f_clamp(in[i], 0.0f, 1.0f);
+			out[i] = WESTON_VEC3F(perceptual_quantizer_inverse(tmp.x),
+					      perceptual_quantizer_inverse(tmp.y),
+					      perceptual_quantizer_inverse(tmp.z));
+		}
+		break;
 	}
 }
 
 /**
-* Given a color curve and a channel, sample an input.
-*
-* This handles the parametric curves (LINPOW, POWLIN, etc) and enumerated color
-* curves. Others should result in failure.
-*
-* @param compositor The Weston compositor
-* @param curve The color curve to be used to sample
-* @param ch The curve color channel to sample from
-* @param len The in and out arrays length
-* @param in The input array to sample
-* @param out The resulting array from sampling
-* @returns True on success, false otherwise
-*/
-bool
+ * Evaluate a color curve on an array
+ *
+ * This handles the parametric curves (LINPOW, POWLIN, etc) and enumerated color
+ * curves. Others result in failure.
+ *
+ * @param compositor The Weston compositor
+ * @param curve The color curve to evaluate
+ * @param in The input array of length @c len .
+ * @param out The output array of length @c len .
+ * @param len The in and out arrays' length.
+ */
+void
 weston_color_curve_sample(struct weston_compositor *compositor,
 			  struct weston_color_curve *curve,
-			  uint32_t ch, uint32_t len, float *in, float *out)
+			  const struct weston_vec3f *in,
+			  struct weston_vec3f *out,
+			  size_t len)
 {
 	struct weston_color_curve_parametric parametric;
 	bool ret;
@@ -193,20 +211,19 @@ weston_color_curve_sample(struct weston_compositor *compositor,
 		 */
 		switch (curve->u.enumerated.tf.info->tf) {
 		case WESTON_TF_ST2084_PQ:
-			sample_pq(curve->u.enumerated.tf_direction, ch, len, in, out);
-			return true;
+			sample_pq(curve->u.enumerated.tf_direction, in, out, len);
+			return;
 		default:
 			ret = weston_color_curve_enum_get_parametric(compositor,
 								     &curve->u.enumerated,
 								     &parametric);
-			if (!ret)
-				return false;
-			goto param;
+			weston_assert_true(compositor, ret);
+			sample_parametric(compositor, &parametric, in, out, len);
+			return;
 		}
 	case WESTON_COLOR_CURVE_TYPE_PARAMETRIC:
-		/* Parametric curve, let's copy it and we'll handle that below. */
-		parametric = curve->u.parametric;
-		goto param;
+		sample_parametric(compositor, &curve->u.parametric, in, out, len);
+		return;
 	case WESTON_COLOR_CURVE_TYPE_IDENTITY:
 		weston_assert_not_reached(compositor,
 					  "no need to sample identity");
@@ -216,19 +233,4 @@ weston_color_curve_sample(struct weston_compositor *compositor,
 	}
 
 	weston_assert_not_reached(compositor, "unknown color curve");
-
-param:
-	/* Sample from parametric curves. */
-	switch (parametric.type) {
-	case WESTON_COLOR_CURVE_PARAMETRIC_TYPE_LINPOW:
-		sample_linpow(&parametric.params.chan[ch],
-			      len, parametric.clamped_input, in, out);
-		return true;
-	case WESTON_COLOR_CURVE_PARAMETRIC_TYPE_POWLIN:
-		sample_powlin(&parametric.params.chan[ch],
-			      len, parametric.clamped_input, in, out);
-		return true;
-	}
-
-	weston_assert_not_reached(compositor, "unknown parametric color curve");
 }

libweston/color-operations.h

@@ -27,10 +27,15 @@
 #define WESTON_COLOR_OPERATIONS_H
 
 #include <libweston/libweston.h>
+#include <libweston/linalg-3.h>
 
-bool
+#include "color.h"
+
+void
 weston_color_curve_sample(struct weston_compositor *compositor,
 			  struct weston_color_curve *curve,
-			  uint32_t ch, uint32_t len, float *in, float *out);
+			  const struct weston_vec3f *in,
+			  struct weston_vec3f *out,
+			  size_t len);
 
 #endif /* WESTON_COLOR_OPERATIONS_H */

libweston/color.c

@@ -354,9 +354,9 @@ weston_color_curve_to_3x1D_LUT(struct weston_compositor *compositor,
 	struct weston_color_curve *curve;
 	float divider = lut_size - 1;
 	const char *step_str;
-	float *in, *lut;
-	unsigned int i, ch;
-	bool ret;
+	float *lut;
+	struct weston_vec3f *tmp;
+	unsigned int i;
 
 	switch(step) {
 	case WESTON_COLOR_CURVE_STEP_PRE:
@@ -389,30 +389,30 @@ weston_color_curve_to_3x1D_LUT(struct weston_compositor *compositor,
 			   "result in bad precision\n", xform->id, step_str);
 	}
 
+	lut = calloc(lut_size, 3 * sizeof *lut);
+	tmp = calloc(lut_size, sizeof *tmp);
+	if (!lut || !tmp) {
+		/* lut_size could be big. */
+		free(lut);
+		free(tmp);
+		str_printf(err_msg, "Out of memory");
+		return NULL;
+	}
+
 	switch(curve->type) {
 	case WESTON_COLOR_CURVE_TYPE_LUT_3x1D:
-		lut = xzalloc(3 * lut_size * sizeof(*lut));
 		curve->u.lut_3x1d.fill_in(xform, lut, lut_size);
+		free(tmp);
 		return lut;
 	case WESTON_COLOR_CURVE_TYPE_ENUM:
 	case WESTON_COLOR_CURVE_TYPE_PARAMETRIC:
-		lut = xzalloc(3 * lut_size * sizeof(*lut));
-		in  = xzalloc(lut_size * sizeof(*lut));
-		for (i = 0; i < lut_size; i++)
-			in[i] = (float)i / divider;
-		for (ch = 0; ch < 3; ch++) {
-			ret = weston_color_curve_sample(compositor, curve, ch, lut_size,
-							in, &lut[ch * lut_size]);
-			if (!ret) {
-				free(lut);
-				lut = NULL;
-				str_printf(err_msg, "can't create color LUT from xform (id %u) " \
-						    "%s-curve, failed to sample color curve",
-						    xform->id, step_str);
-				break;
-			}
+		for (i = 0; i < lut_size; i++) {
+			float x = (float)i / divider;
+			tmp[i] = WESTON_VEC3F(x, x, x);
 		}
-		free(in);
+		weston_color_curve_sample(compositor, curve, tmp, tmp, lut_size);
+		weston_v3f_array_to_planar(lut, tmp, lut_size);
+		free(tmp);
 		return lut;
 	case WESTON_COLOR_CURVE_TYPE_IDENTITY:
 		weston_assert_not_reached(compositor,