Re: [igt-dev] [PATCH i-g-t v3 18/21] lib/igt_frame: Add a checkerboard frame comparison method

Lyude Paul
2019-01-15T22:14:16Z

On Fri, 2019-01-11 at 10:05 +0100, Paul Kocialkowski wrote:
> This introduces a new frame comparison method that was designed for
> patterns that follow a checkerboard style. These patterns are made of
> consecutive rectangular shapes with alternating solid colors. They are
> currently used for some Chamelium-based tests.
>
> The method is particularly adapted for cases where the edges of the
> shapes might be blurred (e.g. due to scaling), which makes it impossible
> to use pixel-perfect or CRC-based comparisons to decide whether the
> captured frame matches the reference.
>
> Overall, this test will first detect the edges of the pattern and later
> exclude them from comparison. Colors are compared between the reference
> and capture with a low threshold for error. A percentage of the faulty
> pixels is calculated and the captured frame is considered invalid if
> more than one percent of the pixels are erroneous.
>
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> ---
> lib/igt_frame.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++++
> lib/igt_frame.h | 2 +
> 2 files changed, 123 insertions(+)
>
> diff --git a/lib/igt_frame.c b/lib/igt_frame.c
> index 6984c02e9912..e0215660ea6e 100644
> --- a/lib/igt_frame.c
> +++ b/lib/igt_frame.c
> @@ -267,3 +267,124 @@ complete:
>
> return match;
> }
> +
> +#define XR24_COLOR_VALUE(data, stride, x, y, c) \
> + *((uint8_t *)(data) + (y) * (stride) + 4 * (x) + (c))
> +
> +/**
> + * igt_check_checkerboard_frame_match:
> + * @reference: The reference cairo surface
> + * @capture: The captured cairo surface
> + *
> + * Checks that the reference frame matches the captured frame using a
> + * method designed for checkerboard patterns. These patterns are made of
> + * consecutive rectangular shapes with alternating solid colors.
> + *
> + * The intent of this method is to cover cases where the captured result is
> + * pixel-perfect due to features such as scaling or YUV conversion and
> + * subsampling. Such effects are mostly noticeable on the edges of the
> + * patterns, so they are detected and excluded from the comparison.
> + *
> + * Returns: a boolean indicating whether the frames match
> + */
> +bool igt_check_checkerboard_frame_match(cairo_surface_t *reference,
> + cairo_surface_t *capture)
> +{
> + unsigned int width, height, ref_stride, cap_stride;
> + void *ref_data, *cap_data;
> + unsigned char *edges_map;
> + unsigned int x, y, c;
> + unsigned int errors = 0, pixels = 0;
> + unsigned int edge_threshold = 100;
> + unsigned int color_error_threshold = 24;
> + double error_rate_threshold = 0.01;
> + double error_rate;
> + unsigned int span = 2;
> + bool match = false;
> +
> + width = cairo_image_surface_get_width(reference);
> + height = cairo_image_surface_get_height(reference);
> +
> + ref_stride = cairo_image_surface_get_stride(reference);
> + ref_data = cairo_image_surface_get_data(reference);
> + igt_assert(ref_data);
> +
> + cap_stride = cairo_image_surface_get_stride(capture);
> + cap_data = cairo_image_surface_get_data(capture);
> + igt_assert(cap_data);
> +
> + edges_map = calloc(1, width * height);
Need an igt_assert here

With that + the documentation changes that Maxime asked for:

Reviewed-by: Lyude Paul <lyude@redhat.com>
> +
> + /* First pass to detect the pattern edges. */
> + for (y = 0; y < height; y++) {
> + if (y < span || y > (height - span - 1))
> + continue;
> +
> + for (x = 0; x < width; x++) {
> + unsigned int xdiff = 0, ydiff = 0;
> +
> + if (x < span || x > (width - span - 1))
> + continue;
> +
> + for (c = 0; c < 3; c++) {
> + xdiff += abs(XR24_COLOR_VALUE(ref_data,
> ref_stride, x + span, y, c) -
> + XR24_COLOR_VALUE(ref_data,
> ref_stride, x - span, y, c));
> + ydiff += abs(XR24_COLOR_VALUE(ref_data,
> ref_stride, x, y + span, c) -
> + XR24_COLOR_VALUE(ref_data,
> ref_stride, x, y - span, c));
> + }
> +
> + edges_map[y * width + x] = (xdiff > edge_threshold ||
> + ydiff > edge_threshold);
> + }
> + }
> +
> + /* Second pass to detect errors. */
> + for (y = 0; y < height; y++) {
> + for (x = 0; x < width; x++) {
> + bool error = false;
> +
> + if (edges_map[y * width + x])
> + continue;
> +
> + for (c = 0; c < 3; c++) {
> + unsigned int diff;
> +
> + /* Compare the reference and capture values.
> */
> + diff = abs(XR24_COLOR_VALUE(ref_data,
> ref_stride, x, y, c) -
> + XR24_COLOR_VALUE(cap_data,
> cap_stride, x, y, c));
> +
> + if (diff > color_error_threshold)
> + error = true;
> + }
> +
> + /* Allow error if coming on or off an edge (on x). */
> + if (error && x >= span && x <= (width - span - 1) &&
> + edges_map[y * width + (x - span)] !=
> + edges_map[y * width + (x + span)])
> + continue;
> +
> + /* Allow error if coming on or off an edge (on y). */
> + if (error && y >= span && y <= (height - span - 1) &&
> + edges_map[(y - span) * width + x] !=
> + edges_map[(y + span) * width + x] && error)
> + continue;
> +
> + if (error)
> + errors++;
> +
> + pixels++;
> + }
> + }
> +
> + free(edges_map);
> +
> + error_rate = (double) errors / pixels;
> +
> + if (error_rate < error_rate_threshold)
> + match = true;
> +
> + igt_debug("Checkerboard pattern %s with error rate %f %%\n",
> + match ? "matched" : "not matched", error_rate * 100);
> +
> + return match;
> +}
> diff --git a/lib/igt_frame.h b/lib/igt_frame.h
> index 11f96cbea203..f44f57d7ce73 100644
> --- a/lib/igt_frame.h
> +++ b/lib/igt_frame.h
> @@ -38,5 +38,7 @@ void igt_write_compared_frames_to_png(cairo_surface_t
> *reference,
> const char *capture_suffix);
> bool igt_check_analog_frame_match(cairo_surface_t *reference,
> cairo_surface_t *capture);
> +bool igt_check_checkerboard_frame_match(cairo_surface_t *reference,
> + cairo_surface_t *capture);
>
> #endif
--
Cheers,
Lyude Paul