sub: reimplement -spugauss as --sub-gauss

Apparently the -spugauss option was popular. The code originally
implementing this is gone (scaler stuff in spudec.c). Reimplement it
using libswscale to scale and blur image subtitles if the --sub-gauss
option is set.

The code does some rather lazy padding to allow the blur to spread
pixels past the original image bounding box. (This problem exists with
normal bilinear scaling too, but is barely noticable.)

Technically, this doesn't just blur subtitles, but anything RGBA (or
indexed) that enters the OSD rendering path. But only image subtitles
produce these OSD formats currently, so no explicit check is done to
prevent blurring in other cases.

1 files changed, 42 insertions, 0 deletions

diff --git a/sub/img_convert.c b/sub/img_convert.c
index e2eded24c3..274a83d833 100644
--- a/sub/img_convert.c
+++ b/sub/img_convert.c
@@ -28,6 +28,7 @@
 #include "video/img_format.h"
 #include "video/mp_image.h"
 #include "video/sws_utils.h"
+#include "video/memcpy_pic.h"
 
 struct osd_conv_cache {
     struct sub_bitmap part;
@@ -86,3 +87,44 @@ bool osd_conv_idx_to_rgba(struct osd_conv_cache *c, struct sub_bitmaps *imgs)
     }
     return true;
 }
+
+bool osd_conv_blur_rgba(struct osd_conv_cache *c, struct sub_bitmaps *imgs,
+                        double gblur)
+{
+    struct sub_bitmaps src = *imgs;
+    if (src.format != SUBBITMAP_RGBA)
+        return false;
+
+    talloc_free(c->parts);
+    imgs->parts = c->parts = talloc_array(c, struct sub_bitmap, src.num_parts);
+
+    for (int n = 0; n < src.num_parts; n++) {
+        struct sub_bitmap *d = &imgs->parts[n];
+        struct sub_bitmap *s = &src.parts[n];
+
+        // add a transparent padding border to reduce artifacts
+        int pad = 5;
+        struct mp_image *temp = alloc_mpi(s->w + pad * 2, s->h + pad * 2,
+                                          IMGFMT_BGRA);
+        memset_pic(temp->planes[0], 0, temp->w * 4, temp->h, temp->stride[0]);
+        uint8_t *p0 = temp->planes[0] + pad * 4 + pad * temp->stride[0];
+        memcpy_pic(p0, s->bitmap, s->w * 4, s->h, temp->stride[0], s->stride);
+
+        double sx = (double)s->dw / s->w;
+        double sy = (double)s->dh / s->h;
+
+        d->x = s->x - pad * sx;
+        d->y = s->y - pad * sy;
+        d->w = d->dw = s->dw + pad * 2 * sx;
+        d->h = d->dh = s->dh + pad * 2 * sy;
+        struct mp_image *image = alloc_mpi(d->w, d->h, IMGFMT_BGRA);
+        talloc_steal(c->parts, image);
+        d->stride = image->stride[0];
+        d->bitmap = image->planes[0];
+
+        mp_image_sw_blur_scale(image, temp, gblur);
+
+        talloc_free(temp);
+    }
+    return true;
+}