path: root/libavfilter/scale.c (plain)
blob: 50cd442849bfd3a161f638e15b3f45b393b25bfe

1	/*
2	* Copyright (c) 2007 Bobby Bingham
3	*
4	* This file is part of FFmpeg.
5	*
6	* FFmpeg is free software; you can redistribute it and/or
7	* modify it under the terms of the GNU Lesser General Public
8	* License as published by the Free Software Foundation; either
9	* version 2.1 of the License, or (at your option) any later version.
10	*
11	* FFmpeg is distributed in the hope that it will be useful,
12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14	* Lesser General Public License for more details.
15	*
16	* You should have received a copy of the GNU Lesser General Public
17	* License along with FFmpeg; if not, write to the Free Software
18	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19	*/
20
21	#include <stdint.h>
22	#include "scale.h"
23	#include "libavutil/eval.h"
24	#include "libavutil/mathematics.h"
25	#include "libavutil/pixdesc.h"
26
27	static const char *const var_names[] = {
28	"PI",
29	"PHI",
30	"E",
31	"in_w", "iw",
32	"in_h", "ih",
33	"out_w", "ow",
34	"out_h", "oh",
35	"a",
36	"sar",
37	"dar",
38	"hsub",
39	"vsub",
40	"ohsub",
41	"ovsub",
42	NULL
43	};
44
45	enum var_name {
46	VAR_PI,
47	VAR_PHI,
48	VAR_E,
49	VAR_IN_W, VAR_IW,
50	VAR_IN_H, VAR_IH,
51	VAR_OUT_W, VAR_OW,
52	VAR_OUT_H, VAR_OH,
53	VAR_A,
54	VAR_SAR,
55	VAR_DAR,
56	VAR_HSUB,
57	VAR_VSUB,
58	VAR_OHSUB,
59	VAR_OVSUB,
60	VARS_NB
61	};
62
63	int ff_scale_eval_dimensions(void *log_ctx,
64	const char *w_expr, const char *h_expr,
65	AVFilterLink *inlink, AVFilterLink *outlink,
66	int *ret_w, int *ret_h)
67	{
68	const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
69	const AVPixFmtDescriptor *out_desc = av_pix_fmt_desc_get(outlink->format);
70	const char *expr;
71	int w, h;
72	int factor_w, factor_h;
73	int eval_w, eval_h;
74	int ret;
75	double var_values[VARS_NB], res;
76
77	var_values[VAR_PI] = M_PI;
78	var_values[VAR_PHI] = M_PHI;
79	var_values[VAR_E] = M_E;
80	var_values[VAR_IN_W] = var_values[VAR_IW] = inlink->w;
81	var_values[VAR_IN_H] = var_values[VAR_IH] = inlink->h;
82	var_values[VAR_OUT_W] = var_values[VAR_OW] = NAN;
83	var_values[VAR_OUT_H] = var_values[VAR_OH] = NAN;
84	var_values[VAR_A] = (double) inlink->w / inlink->h;
85	var_values[VAR_SAR] = inlink->sample_aspect_ratio.num ?
86	(double) inlink->sample_aspect_ratio.num / inlink->sample_aspect_ratio.den : 1;
87	var_values[VAR_DAR] = var_values[VAR_A] * var_values[VAR_SAR];
88	var_values[VAR_HSUB] = 1 << desc->log2_chroma_w;
89	var_values[VAR_VSUB] = 1 << desc->log2_chroma_h;
90	var_values[VAR_OHSUB] = 1 << out_desc->log2_chroma_w;
91	var_values[VAR_OVSUB] = 1 << out_desc->log2_chroma_h;
92
93	/* evaluate width and height */
94	av_expr_parse_and_eval(&res, (expr = w_expr),
95	var_names, var_values,
96	NULL, NULL, NULL, NULL, NULL, 0, log_ctx);
97	eval_w = var_values[VAR_OUT_W] = var_values[VAR_OW] = res;
98
99	if ((ret = av_expr_parse_and_eval(&res, (expr = h_expr),
100	var_names, var_values,
101	NULL, NULL, NULL, NULL, NULL, 0, log_ctx)) < 0)
102	goto fail;
103	eval_h = var_values[VAR_OUT_H] = var_values[VAR_OH] = res;
104	/* evaluate again the width, as it may depend on the output height */
105	if ((ret = av_expr_parse_and_eval(&res, (expr = w_expr),
106	var_names, var_values,
107	NULL, NULL, NULL, NULL, NULL, 0, log_ctx)) < 0)
108	goto fail;
109	eval_w = res;
110
111	w = eval_w;
112	h = eval_h;
113
114	/* Check if it is requested that the result has to be divisible by a some
115	* factor (w or h = -n with n being the factor). */
116	factor_w = 1;
117	factor_h = 1;
118	if (w < -1) {
119	factor_w = -w;
120	}
121	if (h < -1) {
122	factor_h = -h;
123	}
124
125	if (w < 0 && h < 0)
126	eval_w = eval_h = 0;
127
128	if (!(w = eval_w))
129	w = inlink->w;
130	if (!(h = eval_h))
131	h = inlink->h;
132
133	/* Make sure that the result is divisible by the factor we determined
134	* earlier. If no factor was set, it is nothing will happen as the default
135	* factor is 1 */
136	if (w < 0)
137	w = av_rescale(h, inlink->w, inlink->h * factor_w) * factor_w;
138	if (h < 0)
139	h = av_rescale(w, inlink->h, inlink->w * factor_h) * factor_h;
140
141	*ret_w = w;
142	*ret_h = h;
143
144	return 0;
145
146	fail:
147	av_log(log_ctx, AV_LOG_ERROR,
148	"Error when evaluating the expression '%s'.\n"
149	"Maybe the expression for out_w:'%s' or for out_h:'%s' is self-referencing.\n",
150	expr, w_expr, h_expr);
151	return ret;
152	}
153