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png_rgb_to_gray optimization fixes

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This fixes the code that optimizes RGB to Gray transformations that only
selected on channel and clarifies the handling of max_depth in the transform
code.  It eliminates some UNTESTED cases and removes the write 'invert alpha'
UNTESTED macro because, while there are no test cases for it, code review
some months after writing it suggests it is ok.

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler
2015-09-24 17:33:32 -07:00
parent bf51c644f7
commit d394d889e1
5 changed files with 50 additions and 25 deletions
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55
pngtrans.c
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@@ -458,7 +458,7 @@ run_transform_list_forwards(png_transform_controlp tc, png_transformp *start,
/* Called from the init code and below, the caller must initialize 'tc' */
{
png_const_structp png_ptr = tc->png_ptr;
unsigned int max_depth = 0;
unsigned int max_depth = PNG_TC_PIXEL_DEPTH(*tc);
/* Caller guarantees that *start is non-NULL */
debug(*start != NULL);
@@ -494,9 +494,9 @@ run_transform_list_forwards(png_transform_controlp tc, png_transformp *start,
#ifdef PNG_READ_TRANSFORMS_SUPPORTED
unsigned int /* PRIVATE */
png_run_this_transform_list_forwards(png_transform_controlp tc,
png_transformp *start, png_transformp *end)
png_transformp *start, png_transformp end)
{
return run_transform_list_forwards(tc, start, *end);
return run_transform_list_forwards(tc, start, end);
}
#endif /* READ_TRANSFORMS */
@@ -504,18 +504,11 @@ png_run_this_transform_list_forwards(png_transform_controlp tc,
unsigned int /* PRIVATE */
png_run_transform_list_forwards(png_structp png_ptr, png_transform_controlp tc)
{
unsigned int max_depth = PNG_PIXEL_DEPTH(*png_ptr);
if (png_ptr->transform_list != NULL)
{
unsigned int depth =
run_transform_list_forwards(tc, &png_ptr->transform_list, NULL);
return run_transform_list_forwards(tc, &png_ptr->transform_list, NULL);
if (depth > max_depth)
max_depth = depth;
}
return max_depth;
else
return PNG_PIXEL_DEPTH(*png_ptr);
}
#endif /* READ */
@@ -2284,6 +2277,36 @@ png_init_byte_ops(png_transformp *transform, png_transform_controlp tc)
#endif /* SWAP poo */
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
static void
png_init_rgb_to_gray_byte_ops(png_transformp *transform,
png_transform_controlp tc)
{
/* This just delay initializes the function; all the transform initialization
* has been done below.
*/
(*transform)->fn = png_do_byte_ops_up;
/* If this happens on a row do the transform immediately: */
if (!tc->init)
png_do_byte_ops_up(transform, tc);
else
{
/* This doing the init - update the row information here */
# define png_ptr (tc->png_ptr)
png_transform_byte_op *tr =
png_transform_cast(png_transform_byte_op, *transform);
debug(tc->bit_depth == 8U || tc->bit_depth == 16U);
debug((tc->format & PNG_FORMAT_FLAG_COLORMAP) == 0U &&
(tc->format & PNG_FORMAT_FLAG_COLOR) != 0U);
tc->format = tr->format;
tc->bit_depth = tr->bit_depth;
# undef png_ptr
}
}
void /* PRIVATE */
png_add_rgb_to_gray_byte_ops(png_structrp png_ptr, png_transform_controlp tc,
unsigned int index, unsigned int order)
@@ -2294,7 +2317,7 @@ png_add_rgb_to_gray_byte_ops(png_structrp png_ptr, png_transform_controlp tc,
{
png_transform_byte_op *tr = png_transform_cast(png_transform_byte_op,
png_add_transform(png_ptr, sizeof (png_transform_byte_op),
png_do_byte_ops_up, order));
png_init_rgb_to_gray_byte_ops, order));
affirm((tc->format & (PNG_FORMAT_FLAG_COLOR+PNG_FORMAT_FLAG_COLORMAP)) ==
PNG_FORMAT_FLAG_COLOR &&
@@ -2305,11 +2328,8 @@ png_add_rgb_to_gray_byte_ops(png_structrp png_ptr, png_transform_controlp tc,
/* For 1 byte channel [index] plus, maybe, alpha: */
if (tc->bit_depth == 8)
{
tr->codes = 8U + index +
((tc->format & PNG_FORMAT_FLAG_ALPHA) != 0 ? (8U+3U) << 4 : 0U);
UNTESTED
}
else
{
@@ -2320,7 +2340,6 @@ png_add_rgb_to_gray_byte_ops(png_structrp png_ptr, png_transform_controlp tc,
tr->codes = (8U + index) + ((9U + index) << 4) +
((tc->format & PNG_FORMAT_FLAG_ALPHA) != 0 ?
((8U+6U) + ((9U+6U) << 4)) << 8 : 0U);
UNTESTED
}
}
#endif /* READ_RGB_TO_GRAY */