scale.c

   1 #include <caml/fail.h>
   2 #include <caml/alloc.h>
   3 #include <caml/memory.h>
   4
   5 #include <libswscale/swscale.h>
   6
   7 typedef struct {
   8     int w, h;
   9     int out_w, out_h;
  10     int pitch;
  11     struct SwsContext *sws;
  12     int linesize[3];
  13     int offset[3];
  14     int outsize;
  15 } State;
  16
  17 static State glob_state;
  18
  19 static void sws_reset (State *s)
  20 {
  21 #ifdef ARCH_BIG_ENDIAN
  22     int fmt = PIX_FMT_RGB565BE;
  23 #else
  24     int fmt = PIX_FMT_RGB565LE;
  25 #endif
  26
  27     if (s->sws) {
  28         sws_freeContext (s->sws);
  29         s->sws = NULL;
  30     }
  31
  32     s->sws = sws_getContext (s->w, s->h, fmt,
  33                              s->out_w, s->out_h, PIX_FMT_YUV420P,
  34                              SWS_BICUBIC,
  35                              NULL, NULL, NULL);
  36     if (!s->sws)
  37         caml_failwith ("sws_getContext failed");
  38 }
  39
  40 static void scale (State *s, uint8_t *in, uint8_t *out)
  41 {
  42     int ret;
  43     uint8_t *plane[3];
  44
  45     plane[0] = out;
  46     plane[1] = plane[0] + s->offset[1];
  47     plane[2] = plane[1] + s->offset[2];
  48
  49     ret = sws_scale (s->sws, &in, &s->pitch,
  50                      0, s->h, plane, s->linesize);
  51     if (ret != s->out_h)
  52         caml_failwith ("sws_scale failed");
  53 }
  54
  55 CAMLprim value ml_scale_reset (value params_v)
  56 {
  57     CAMLparam1 (params_v);
  58     State *s = &glob_state;
  59
  60     s->w = Int_val (Field (params_v, 0));
  61     s->h = Int_val (Field (params_v, 1));
  62     s->out_w = Int_val (Field (params_v, 2));
  63     s->out_h = Int_val (Field (params_v, 3));
  64     s->pitch = Int_val (Field (params_v, 4));
  65
  66     s->outsize = s->out_w * s->out_h * 3 / 2;
  67
  68     s->linesize[0] = s->out_w;
  69     s->linesize[1] = s->out_w / 2;
  70     s->linesize[2] = s->out_w / 2;
  71
  72     s->offset[0] = 0;
  73     s->offset[1] = s->out_w * s->out_h;
  74     s->offset[2] = s->offset[1] / 4;
  75
  76     sws_reset (s);
  77
  78     CAMLreturn (Val_int (s->outsize));
  79 }
  80
  81 CAMLprim value ml_scale (value in_v, value out_v)
  82 {
  83     CAMLparam2 (in_v, out_v);
  84     State *s = &glob_state;
  85
  86     scale (s, String_val (in_v), String_val (out_v));
  87     CAMLreturn (Val_unit);
  88 }