diff options
| author | Jeremy Kerr <jk@ozlabs.org> | 2007-01-12 18:32:10 +1100 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2007-01-22 14:26:14 +1100 |
| commit | 7aaf0c93b6030b9789ae481a9a6d1155a9f74ec1 (patch) | |
| tree | 010df1b67df34d5b9c3e7a4840b10817717ad884 | |
| parent | c48266b56e7da69fe94785b62ac275517cf33f97 (diff) | |
Premultiply alpha channel on PNG images
libtwin expects pixmaps to be premultiplied with their alpha channel,
but loaded PNGs aren't. This change adds a generic function to do alpha
premulitplication, and uses it on pixmaps loaded from PNG.
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
| -rw-r--r-- | libtwin/twin.h | 2 | ||||
| -rw-r--r-- | libtwin/twin_draw.c | 24 | ||||
| -rw-r--r-- | libtwin/twin_png.c | 3 |
3 files changed, 29 insertions, 0 deletions
diff --git a/libtwin/twin.h b/libtwin/twin.h index 065cdc9..04a9ac6 100644 --- a/libtwin/twin.h +++ b/libtwin/twin.h @@ -647,6 +647,8 @@ twin_fill (twin_pixmap_t *dst, twin_coord_t right, twin_coord_t bottom); +void +twin_premultiply_alpha (twin_pixmap_t *px); /* * twin_cursor.c */ diff --git a/libtwin/twin_draw.c b/libtwin/twin_draw.c index 1c117a0..3b19984 100644 --- a/libtwin/twin_draw.c +++ b/libtwin/twin_draw.c @@ -641,6 +641,30 @@ void twin_composite (twin_pixmap_t *dst, operator, width, height); } +void twin_premultiply_alpha(twin_pixmap_t *px) +{ + int x, y; + twin_pointer_t p; + uint16_t t1, t2, t3; + + if (px->format != TWIN_ARGB32) + return; + + for (y = 0; y < px->height; y++) { + p.b = px->p.b + y * px->stride; + + for (x = 0; x < px->width; x++) { + twin_argb32_t v = p.argb32[x]; + twin_a8_t a = twin_get_8(v, 24); + + p.argb32[x] = (v & 0xff000000) | + twin_int_mult(twin_get_8(v, 16), a, t1) << 16 | + twin_int_mult(twin_get_8(v, 8), a, t2) << 8 | + twin_int_mult(twin_get_8(v, 0), a, t3); + } + } +} + /* * array primary index is OVER SOURCE * array secondary index is ARGB32 RGB16 A8 diff --git a/libtwin/twin_png.c b/libtwin/twin_png.c index afe492a..05bbd04 100644 --- a/libtwin/twin_png.c +++ b/libtwin/twin_png.c @@ -172,6 +172,9 @@ twin_pixmap_t *twin_png_to_pixmap(const char *filepath, twin_format_t fmt) png_read_end(png, NULL); + if (fmt == TWIN_ARGB32) + twin_premultiply_alpha(pix); + fail_free: if (rowp) free(rowp); |