samples: video: capture: Enhance fixture test with colorbar checking

Currently, the camera fixture test can only tell whether data are dumped
onto memory. This is to check further if the image content is correct.

The algorithm is rather simple: compare the average color of each bar
of a generated pattern with a predefined target in CIELAB76 color
space (which is nearly perceptually uniform).

Signed-off-by: Phi Bang Nguyen <phibang.nguyen@nxp.com>

Author: ngphibang

samples/drivers/video/capture/sample.yaml

@@ -12,6 +12,7 @@ tests:
       - platform:mimxrt1170_evk@B/mimxrt1176/cm7:SHIELD="nxp_btb44_ov5640;rk055hdmipi4ma0"
     extra_configs:
       - CONFIG_TEST=y
+      - CONFIG_FPU=y
     harness: console
     harness_config:
       fixture: fixture_camera
@@ -21,6 +22,7 @@ tests:
         - "Got frame \\d+"
         - "size: \\d+;"
         - "timestamp \\d+"
+        - "Pattern OK"
     platform_allow:
       - arduino_nicla_vision/stm32h747xx/m7
       - mimxrt1064_evk

samples/drivers/video/capture/src/check_test_pattern.h

@@ -0,0 +1,154 @@
+/*
+ * Copyright 2024 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef TEST_PATTERN_CHECK_H_
+#define TEST_PATTERN_CHECK_H_
+
+#include <math.h>
+
+#include <zephyr/drivers/video.h>
+
+#define LAB_THRESHOLD 10.0
+
+#define BARS_NUM   8
+#define PIXELS_NUM 5
+
+typedef struct {
+	double L;
+	double a;
+	double b;
+} CIELAB;
+
+/*
+ * This is measured on a real 8-colorbar pattern generated by an ov5640 camera sensor.
+ * For other sensors, it can be slightly different. If it doesn't fit anymore, either
+ * this array or the LAB_THRESHOLD can be modified.
+ *
+ * {White, Yellow, Cyan, Green, Magenta, Red, Blue, Black}
+ */
+static const CIELAB colorbars_target[] = {
+	{100.0, 0.0053, -0.0104},     {97.1804, -21.2151, 91.3538}, {90.1352, -58.4675, 6.0570},
+	{87.7630, -85.9469, 83.2128}, {56.6641, 95.0182, -66.9129}, {46.6937, 72.7494, 49.5801},
+	{27.6487, 71.5662, -97.4712}, {1.3726, -2.8040, 2.0043}};
+
+static inline CIELAB rgb888_to_lab(const uint8_t r, const uint8_t g, const uint8_t b)
+{
+	CIELAB lab;
+
+	double r_lin = r / 255.0;
+	double g_lin = g / 255.0;
+	double b_lin = b / 255.0;
+
+	r_lin = r_lin > 0.04045 ? pow((r_lin + 0.055) / 1.055, 2.4) : r_lin / 12.92;
+	g_lin = g_lin > 0.04045 ? pow((g_lin + 0.055) / 1.055, 2.4) : g_lin / 12.92;
+	b_lin = b_lin > 0.04045 ? pow((b_lin + 0.055) / 1.055, 2.4) : b_lin / 12.92;
+
+	double x = r_lin * 0.4124 + g_lin * 0.3576 + b_lin * 0.1805;
+	double y = r_lin * 0.2126 + g_lin * 0.7152 + b_lin * 0.0722;
+	double z = r_lin * 0.0193 + g_lin * 0.1192 + b_lin * 0.9505;
+
+	x /= 0.95047;
+	z /= 1.08883;
+
+	x = x > 0.008856 ? pow(x, 1.0 / 3.0) : (7.787 * x) + (16.0 / 116.0);
+	y = y > 0.008856 ? pow(y, 1.0 / 3.0) : (7.787 * y) + (16.0 / 116.0);
+	z = z > 0.008856 ? pow(z, 1.0 / 3.0) : (7.787 * z) + (16.0 / 116.0);
+
+	lab.L = 116.0 * y - 16.0;
+	lab.a = 500.0 * (x - y);
+	lab.b = 200.0 * (y - z);
+
+	return lab;
+}
+
+static inline CIELAB xrgb32_to_lab(const uint32_t color)
+{
+	uint8_t r = (color >> 16) & 0xFF;
+	uint8_t g = (color >> 8) & 0xFF;
+	uint8_t b = color & 0xFF;
+
+	return rgb888_to_lab(r, g, b);
+}
+
+static inline CIELAB rgb565_to_lab(const uint16_t color)
+{
+	uint8_t r5 = (color >> 11) & 0x1F;
+	uint8_t g6 = (color >> 5) & 0x3F;
+	uint8_t b5 = color & 0x1F;
+
+	/* Convert RGB565 to RGB888 */
+	uint8_t r = (r5 * 255) / 31;
+	uint8_t g = (g6 * 255) / 63;
+	uint8_t b = (b5 * 255) / 31;
+
+	return rgb888_to_lab(r, g, b);
+}
+
+static inline void sum_lab(CIELAB *sum, const CIELAB lab)
+{
+	sum->L += lab.L;
+	sum->a += lab.a;
+	sum->b += lab.b;
+}
+
+static inline void average_lab(CIELAB *lab, const uint32_t count)
+{
+	if (count > 0) {
+		lab->L /= count;
+		lab->a /= count;
+		lab->b /= count;
+	}
+}
+
+static inline double deltaE(const CIELAB lab1, const CIELAB lab2)
+{
+	return sqrt(pow(lab1.L - lab2.L, 2) + pow(lab1.a - lab2.a, 2) + pow(lab1.b - lab2.b, 2));
+}
+
+/*
+ * As color values may vary near the boundary of each bar and also, for computational
+ * efficiency, check only a small number of pixels (PIXELS_NUM) in the middle of each bar.
+ */
+static inline bool is_colorbar_ok(const uint8_t *const buf, const struct video_format fmt)
+{
+	int i;
+	int bw = fmt.width / BARS_NUM;
+	CIELAB colorbars[BARS_NUM] = {0};
+
+	for (int h = 0; h < fmt.height; h++) {
+		for (i = 0; i < BARS_NUM; i++) {
+			if (fmt.pixelformat == VIDEO_PIX_FMT_XRGB32) {
+				uint32_t *pixel =
+					(uint32_t *)&buf[4 * (h * fmt.width + bw / 2 + i * bw)];
+
+				for (int j = -PIXELS_NUM / 2; j <= PIXELS_NUM / 2; j++) {
+					sum_lab(&colorbars[i], xrgb32_to_lab(*(pixel + j)));
+				}
+			} else if (fmt.pixelformat == VIDEO_PIX_FMT_RGB565) {
+				uint16_t *pixel =
+					(uint16_t *)&buf[2 * (h * fmt.width + bw / 2 + i * bw)];
+
+				for (int j = -PIXELS_NUM / 2; j <= PIXELS_NUM / 2; j++) {
+					sum_lab(&colorbars[i], rgb565_to_lab(*(pixel + j)));
+				}
+			} else {
+				printk("Format %d is not supported", fmt.pixelformat);
+				return false;
+			}
+		}
+	}
+
+	for (i = 0; i < BARS_NUM; i++) {
+		average_lab(&colorbars[i], PIXELS_NUM * fmt.height);
+		if (deltaE(colorbars[i], colorbars_target[i]) > LAB_THRESHOLD) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
+#endif /* TEST_PATTERN_CHECK_H_ */

samples/drivers/video/capture/src/main.c

@@ -10,15 +10,19 @@
 #include <zephyr/drivers/display.h>
 #include <zephyr/drivers/video.h>
 
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(main);
+
 #ifdef CONFIG_TEST
+#include <zephyr/drivers/video-controls.h>
+
+#include "check_test_pattern.h"
+
 #define LOG_LEVEL LOG_LEVEL_DBG
 #else
 #define LOG_LEVEL CONFIG_LOG_DEFAULT_LEVEL
 #endif
 
-#include <zephyr/logging/log.h>
-LOG_MODULE_REGISTER(main);
-
 #define VIDEO_DEV_SW "VIDEO_SW_GENERATOR"
 
 #if DT_HAS_CHOSEN(zephyr_display)
@@ -175,6 +179,10 @@ int main(void)
 		fie.index++;
 	}
 
+#ifdef CONFIG_TEST
+	video_set_ctrl(video_dev, VIDEO_CID_CAMERA_TEST_PATTERN, (void *)1);
+#endif
+
 #if DT_HAS_CHOSEN(zephyr_display)
 	const struct device *const display_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_display));
 
@@ -231,6 +239,12 @@ int main(void)
 		LOG_DBG("Got frame %u! size: %u; timestamp %u ms", frame++, vbuf->bytesused,
 		       vbuf->timestamp);
 
+#ifdef CONFIG_TEST
+		if (is_colorbar_ok(vbuf->buffer, fmt)) {
+			LOG_DBG("Pattern OK!\n");
+		}
+#endif
+
 #if DT_HAS_CHOSEN(zephyr_display)
 		video_display_frame(display_dev, vbuf, fmt);
 #endif