[hackers] [blind] blind-spiral-gradient: add -t || Mattias Andrée

[git]

commit e7f1780c5c05840ec3eca54b83d76c2658bf5de8
Author:     Mattias Andrée <maand...@kth.se>
AuthorDate: Tue Jul 11 21:40:43 2017 +0200
Commit:     Mattias Andrée <maand...@kth.se>
CommitDate: Tue Jul 11 21:40:43 2017 +0200

    blind-spiral-gradient: add -t
    
    Signed-off-by: Mattias Andrée <maand...@kth.se>

diff --git a/man/blind-spiral-gradient.1 b/man/blind-spiral-gradient.1
index 954adcc..efd61f3 100644
--- a/man/blind-spiral-gradient.1
+++ b/man/blind-spiral-gradient.1
@@ -4,7 +4,8 @@ blind-spiral-gradient - Generate a video with a spiral gradient
 .SH SYNOPSIS
 .B blind-spiral-gradient
 [-s
-.IR spirals ]
+.I spirals
+| -t]
 [-al]
 -w
 .I width
@@ -112,11 +113,31 @@ distributed.
 .I spirals
 can be any non-zero real number.
 .TP
+.B -t
+Base the resulting values only on the angle
+in the spiral formula rather than then both
+the angle and radius. This is useful for
+creating transitions with spiral effects.
+.TP
 .BR -w " "\fIwidth\fP
 The width of the video, in pixels.
 .TP
 .BR -h " "\fIheight\fP
 The height of the video, in pixels.
+.SH NOTES
+Because
+.B -s
+has no affect when
+.B -t
+is applied,
+.B -s
+and
+.B -t
+cannot be combined unless
+.I spirals
+is 1. This will change in the future
+if a way to meaningfully combined the
+two flags is found.
 .SH SEE ALSO
 .BR blind (7),
 .BR blind-from-text (7),
diff --git a/src/blind-spiral-gradient.c b/src/blind-spiral-gradient.c
index 5d80bef..1eb71bd 100644
--- a/src/blind-spiral-gradient.c
+++ b/src/blind-spiral-gradient.c
@@ -1,10 +1,11 @@
 /* See LICENSE file for copyright and license details. */
 #include "common.h"
 
-USAGE("[-s spirals] [-al] -w width -h height")
+USAGE("[-s spirals | t] [-al] -w width -h height")
 
 static int anticlockwise = 0;
 static int logarithmic = 0;
+static int angle = 0;
 static double spirals = 1;
 static size_t width = 0;
 static size_t height = 0;
@@ -98,7 +99,10 @@ static int with_vector;
                                                r = pow(r / b, ep);\
                                                r = (r - v) / (2 * (TYPE)M_PI);\
                                        }\
-                                       r = mod(r, 1 / (TYPE)spirals) * 
(TYPE)spirals + r - mod(r, (TYPE)1);\
+                                       if (angle)\
+                                               r = (int)(r + 1) + v / (2 * 
(TYPE)M_PI);\
+                                       else\
+                                               r = mod(r, 1 / (TYPE)spirals) * 
(TYPE)spirals + r - mod(r, (TYPE)1);\
                                        buf[ptr][0] = buf[ptr][1] = buf[ptr][2] 
= buf[ptr][3] = r;\
                                        if (++ptr == ELEMENTSOF(buf)) {\
                                                ewriteall(STDOUT_FILENO, buf, 
sizeof(buf), "<stdout>");\
@@ -131,6 +135,9 @@ main(int argc, char *argv[])
                if (!spirals)
                        eprintf("the value of -s must not be 0");
                break;
+       case 't':
+               angle = 1;
+               break;
        case 'w':
                width = etozu_flag('w', UARGF(), 1, SIZE_MAX);
                break;
@@ -141,7 +148,7 @@ main(int argc, char *argv[])
                usage();
        } ARGEND;
 
-       if (!width || !height || argc)
+       if (!width || !height || argc || (spirals != 1 && angle))
                usage();
 
        eopen_stream(&stream, NULL);