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	Add blind-find-rectangle - blind - suckless command-line video editing utility
	git clone git://git.suckless.org/blind
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	---
	commit b87d6efb6fdca579c23020a93212f8f35375e1fe
	parent 533819598030141394a67cb8b80047622c478f44
	Author: Mattias Andrée <[email protected]>
	Date: Sun, 4 Jun 2017 16:46:14 +0200

	Add blind-find-rectangle

	Signed-off-by: Mattias Andrée <[email protected]>

	Diffstat:
	M Makefile \| 1 +
	M README \| 3 +++
	A man/blind-find-rectangle.1 \| 70 +++++++++++++++++++++++++++++…
	M man/blind.7 \| 3 +++
	A src/blind-find-rectangle.c \| 135 +++++++++++++++++++++++++++++…

	5 files changed, 212 insertions(+), 0 deletions(-)
	---
	diff --git a/Makefile b/Makefile
	@@ -16,6 +16,7 @@ BIN =\
	blind-disperse\
	blind-dissolve\
	blind-extend\
	+ blind-find-rectangle\
	blind-flip\
	blind-flop\
	blind-from-image\
	diff --git a/README b/README
	@@ -48,6 +48,9 @@ UTILITIES
	blind-extend(1)
	Add margins to a video

	+ blind-find-rectangle(1)
	+ Locate a coloured rectangle
	+
	blind-flip(1)
	Mirror a video vertically

	diff --git a/man/blind-find-rectangle.1 b/man/blind-find-rectangle.1
	@@ -0,0 +1,70 @@
	+.TH BLIND-FIND-RECTANGLE 1 blind
	+.SH NAME
	+blind-find-rectangle - Locate a coloured rectangle
	+.SH SYNOPSIS
	+.B blind-find-rectangle
	+[-a
	+.IR min-area ]
	+[-h
	+.IR min-height ]
	+[-w
	+.IR min-width ]
	+.I X
	+.I Y
	+.I Z
	+.RI [ alpha ]
	+.SH DESCRIPTION
	+.B blind-find-rectangle
	+reads a video from stdin, and locates the largest
	+rectangle of a specified colour. If there are two
	+or more maximal rectangles, one is choosen arbitrarily.
	+The specified by the arguments
	+.IR X ,
	+.IR Y ,
	+and
	+.IR Z ,
	+and the selected
	+.I alpha
	+value. The colour is specified in CIE XYZ. If
	+.I X
	+and
	+.I Z
	+are not specified, the colour will be CIE Standard Illuminant
	+D65-grey with the luminosity
	+.IR Y .
	+If
	+.I alpha
	+is not specified, 1, which means fully opaque, will be used.
	+.SH STDOUT
	+The location and dimensions of the rectangle is printed stdout.
	+Exactly one line is printed per frame. Each line has the format
	+.nf
	+
	+ \fB"%zu %zu %zu %zu\\n"\fP, <\fIleft\fP>, <\fItop\fP>, <\fIwidth\fP>, …
	+
	+.fi
	+where
	+.I left
	+is position on the X-axis (measured from the left) on the
	+left-most pixels in the rectangle,
	+.I top
	+is position on the Y-axis (measured from the top) on the
	+top-most pixels in the rectangle,
	+.I width
	+is the width of the rectangle, and
	+.I height
	+is the width of the rectangle.
	+.SH NOTES
	+.B blind-find-rectangle
	+may be changed in the future to use some other colour model,
	+therefore, it is recommended to also use
	+.BR blind-colour-ciexyz (1)
	+if you are specifying the colour in CIE XYZ. If however
	+your values are colour space-agnostic, you should not.
	+.SH SEE ALSO
	+.BR blind (7),
	+.BR blind-colour-ciexyz (1),
	+.BR blind-colour-srgb (1)
	+.SH AUTHORS
	+Mattias Andrée
	+.RI < [email protected] >
	diff --git a/man/blind.7 b/man/blind.7
	@@ -61,6 +61,9 @@ Framewise split a video into multiple videos
	.BR blind-extend (1)
	Add margins to a video
	.TP
	+.BR blind-find-rectangle (1)
	+Locate a coloured rectangle
	+.TP
	.BR blind-flip (1)
	Mirror a video vertically
	.TP
	diff --git a/src/blind-find-rectangle.c b/src/blind-find-rectangle.c
	@@ -0,0 +1,135 @@
	+/* See LICENSE file for copyright and license details. */
	+#include "common.h"
	+
	+USAGE("[-a min-area] [-h min-height] [-w min-width] X Y Z [alpha]")
	+
	+struct pair {
	+ size_t x;
	+ size_t w;
	+};
	+
	+static struct stream stream;
	+static double X, Y, Z, alpha = 1;
	+static size_t min_width = 1;
	+static size_t min_height = 1;
	+static size_t min_area = 1;
	+static struct pair *stack = NULL;
	+static size_t *cache = NULL;
	+static char *buf = NULL;
	+
	+static void
	+process(const void *colour)
	+{
	+ size_t y, x, x0, w, w0, h, top, area;
	+ size_t best_area, x1, x2, y1, y2;
	+ for (;;) {
	+ top = x1 = x2 = y1 = y2 = best_area = 0;
	+ memset(cache, 0, (stream.width + 1) * sizeof(*cache));
	+ for (y = 0; eread_row(&stream, buf); y++) {
	+ w = 0;
	+ for (x = 0; x <= stream.width; x++) {
	+ if (x != stream.width) {
	+ if (!memcmp(buf + x * stream.pixel_siz…
	+ cache[x] += 1;
	+ else
	+ cache[x] = 0;
	+ }
	+ if (cache[x] > w) {
	+ stack[top].x = x;
	+ stack[top++].w = w;
	+ w = cache[x];
	+ } else if (cache[x] < w) {
	+ do {
	+ x0 = stack[--top].x;
	+ w0 = stack[top].w;
	+ area = w * (x - x0);
	+ if (area > best_area) {
	+ best_area = area;
	+ x1 = x0;
	+ x2 = x - 1;
	+ y1 = y - w + 1;
	+ y2 = y;
	+ }
	+ w = w0;
	+ } while (cache[x] < w);
	+ if ((w = cache[x])) {
	+ stack[top].x = x0;
	+ stack[top++].w = w0;
	+ }
	+ }
	+ }
	+ fprintf(stderr, "%zu\n", y);
	+ }
	+ if (!y)
	+ break;
	+ w = x2 - x1 + 1;
	+ h = y2 - y1 + 1;
	+ if (best_area < min_area \|\| w < min_width \|\| h < min_height)
	+ printf("0 0 0 0\n");
	+ else
	+ printf("%zu %zu %zu %zu\n", x1, y1, w, h);
	+ }
	+}
	+
	+int
	+main(int argc, char *argv[])
	+{
	+ double colour_lf[4];
	+ double colour_f[4];
	+
	+ ARGBEGIN {
	+ case 'a':
	+ min_area = etozu_flag('a', UARGF(), 1, SIZE_MAX);
	+ break;
	+ case 'h':
	+ min_height = etozu_flag('h', UARGF(), 1, SIZE_MAX);
	+ break;
	+ case 'w':
	+ min_width = etozu_flag('w', UARGF(), 1, SIZE_MAX);
	+ break;
	+ default:
	+ usage();
	+ } ARGEND;
	+
	+ if (argc != 3 && argc != 4)
	+ usage();
	+
	+ X = etolf_arg("the X value", argv[0]);
	+ Y = etolf_arg("the Y value", argv[1]);
	+ Z = etolf_arg("the Z value", argv[2]);
	+ if (argc > 3)
	+ alpha = etolf_arg("the alpha value", argv[3]);
	+
	+ eopen_stream(&stream, NULL);
	+ echeck_dimensions(&stream, WIDTH, NULL);
	+ if (stream.width == SIZE_MAX)
	+ eprintf("video is too wide\n");
	+ if (stream.width > SIZE_MAX / stream.height)
	+ eprintf("video is too large\n");
	+
	+ stack = emalloc2(stream.width + 1, sizeof(*stack));
	+ cache = emalloc2(stream.width + 1, sizeof(*cache));
	+ buf = emalloc(stream.row_size);
	+
	+ if (!strcmp(stream.pixfmt, "xyza")) {
	+ colour_lf[0] = X;
	+ colour_lf[1] = Y;
	+ colour_lf[2] = Z;
	+ colour_lf[3] = alpha;
	+ process(colour_lf);
	+ } else if (!strcmp(stream.pixfmt, "xyza f")) {
	+ colour_f[0] = (float)X;
	+ colour_f[1] = (float)Y;
	+ colour_f[2] = (float)Z;
	+ colour_f[3] = (float)alpha;
	+ process(colour_f);
	+ } else {
	+ eprintf("pixel format %s is not supported, try xyza\n", stream…
	+ }
	+
	+ fshut(stdout, "<stdout>");
	+ free(stack);
	+ free(cache);
	+ free(buf);
	+ return 0;
	+}