mp_image: add mp_image_crop()

Actually stolen from draw_bmp.c.

4 files changed, 33 insertions, 0 deletions

diff --git a/video/img_format.c b/video/img_format.c
index 8a286be9fc..a6d92f1a1f 100644
--- a/video/img_format.c
+++ b/video/img_format.c
@@ -210,6 +210,12 @@ static struct mp_imgfmt_desc get_avutil_fmt(enum PixelFormat fmt)
         desc.ys[p] = (p == 1 || p == 2) ? desc.chroma_ys : 0;
     }
 
+    desc.align_x = 1 << desc.chroma_xs;
+    desc.align_y = 1 << desc.chroma_ys;
+
+    if ((desc.bpp[0] % 8) != 0)
+        desc.align_x = 8 / desc.bpp[0]; // expect power of 2
+
     return desc;
 }
 
diff --git a/video/img_format.h b/video/img_format.h
index f67971e5c6..37ac32ffac 100644
--- a/video/img_format.h
+++ b/video/img_format.h
@@ -64,6 +64,8 @@ struct mp_imgfmt_desc {
     int flags;              // MP_IMGFLAG_* bitfield
     int8_t num_planes;
     int8_t chroma_xs, chroma_ys; // chroma shift (i.e. log2 of chroma pixel size)
+    int8_t align_x, align_y;     // pixel size to get byte alignment and to get
+                                 // to a pixel pos where luma & chroma aligns
     int8_t avg_bpp;
     int8_t bytes[MP_MAX_PLANES]; // bytes per pixel (MP_IMGFLAG_BYTE_ALIGNED)
     int8_t bpp[MP_MAX_PLANES];   // bits per pixel
diff --git a/video/mp_image.c b/video/mp_image.c
index 4df4d2e17f..256e908198 100644
--- a/video/mp_image.c
+++ b/video/mp_image.c
@@ -335,6 +335,28 @@ void mp_image_copy_attributes(struct mp_image *dst, struct mp_image *src)
     }
 }
 
+// Crop the given image to (x0, y0)-(x1, y1) (bottom/right border exclusive)
+// x0/y0 must be naturally aligned.
+void mp_image_crop(struct mp_image *img, int x0, int y0, int x1, int y1)
+{
+    assert(x0 >= 0 && y0 >= 0);
+    assert(x0 <= x1 && y0 <= y1);
+    assert(x1 <= img->w && y1 <= img->h);
+    assert(!(x0 & (img->fmt.align_x - 1)));
+    assert(!(y0 & (img->fmt.align_y - 1)));
+
+    for (int p = 0; p < img->num_planes; ++p) {
+        img->planes[p] += (y0 >> img->fmt.ys[p]) * img->stride[p] +
+                          (x0 >> img->fmt.xs[p]) * img->fmt.bpp[p] / 8;
+    }
+    mp_image_set_size(img, x1 - x0, y1 - y0);
+}
+
+void mp_image_crop_rc(struct mp_image *img, struct mp_rect rc)
+{
+    mp_image_crop(img, rc.x0, rc.y0, rc.x1, rc.y1);
+}
+
 void mp_image_clear(struct mp_image *mpi, int x0, int y0, int w, int h)
 {
     int y;
diff --git a/video/mp_image.h b/video/mp_image.h
index 1d00115545..efbb7551b3 100644
--- a/video/mp_image.h
+++ b/video/mp_image.h
@@ -102,6 +102,9 @@ void mp_image_make_writeable(struct mp_image *img);
 void mp_image_setrefp(struct mp_image **p_img, struct mp_image *new_value);
 void mp_image_unrefp(struct mp_image **p_img);
 
+void mp_image_crop(struct mp_image *img, int x0, int y0, int x1, int y1);
+void mp_image_crop_rc(struct mp_image *img, struct mp_rect rc);
+
 void mp_image_set_size(struct mp_image *mpi, int w, int h);
 void mp_image_set_display_size(struct mp_image *mpi, int dw, int dh);