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[libpng15] Simplified read/write API initial version; basic read/write tested
on a variety of images, limited documentation (in the header file.)
This commit is contained in:
John Bowler
committed by
Glenn Randers-Pehrson
Glenn Randers-Pehrson
parent
92a1d46c8d
commit
7875d534cb
47
pngrutil.c
47
pngrutil.c
@@ -2767,18 +2767,13 @@ png_check_chunk_name(png_structp png_ptr, png_uint_32 chunk_name)
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}
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}
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/* Combines the row recently read in with the existing pixels in the
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* row. This routine takes care of alpha and transparency if requested.
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* This routine also handles the two methods of progressive display
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* of interlaced images, depending on the mask value.
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* The mask value describes which pixels are to be combined with
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* the row. The pattern always repeats every 8 pixels, so just 8
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* bits are needed. A one indicates the pixel is to be combined,
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* a zero indicates the pixel is to be skipped. This is in addition
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* to any alpha or transparency value associated with the pixel. If
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* you want all pixels to be combined, pass 0xff (255) in mask.
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/* Combines the row recently read in with the existing pixels in the row. This
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* routine takes care of alpha and transparency if requested. This routine also
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* handles the two methods of progressive display of interlaced images,
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* depending on the 'display' value; if 'display' is true then the whole row
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* (dp) is filled from the start by replicating the available pixels. If
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* 'display' is false only those pixels present in the pass are filled in.
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*/
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void /* PRIVATE */
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png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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{
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@@ -2850,7 +2845,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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if (pixel_depth < 8)
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{
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/* For pixel depths up to 4-bpp the 8-pixel mask can be expanded to fit
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/* For pixel depths up to 4 bpp the 8-pixel mask can be expanded to fit
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* into 32 bits, then a single loop over the bytes using the four byte
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* values in the 32-bit mask can be used. For the 'display' option the
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* expanded mask may also not require any masking within a byte. To
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@@ -2859,7 +2854,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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*
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* The 'regular' case requires a mask for each of the first 6 passes,
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* the 'display' case does a copy for the even passes in the range
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* 0..6. This has already been handled in the tst above.
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* 0..6. This has already been handled in the test above.
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*
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* The masks are arranged as four bytes with the first byte to use in
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* the lowest bits (little-endian) regardless of the order (PACKSWAP or
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@@ -2867,7 +2862,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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*
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* NOTE: the whole of this logic depends on the caller of this function
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* only calling it on rows appropriate to the pass. This function only
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* understands the 'x' logic, the 'y' logic is handled by the caller.
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* understands the 'x' logic; the 'y' logic is handled by the caller.
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*
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* The following defines allow generation of compile time constant bit
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* masks for each pixel depth and each possibility of swapped or not
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@@ -2885,7 +2880,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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* the compiler even though it isn't used. Microsoft Visual C (various
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* versions) and the Intel C compiler are known to do this. To avoid
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* this the following macros are used in 1.5.6. This is a temporary
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* solution to avoid destablizing the code during the release process.
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* solution to avoid destabilizing the code during the release process.
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*/
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# if PNG_USE_COMPILE_TIME_MASKS
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# define PNG_LSR(x,s) ((x)>>((s) & 0x1f))
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@@ -2930,7 +2925,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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#if PNG_USE_COMPILE_TIME_MASKS
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/* Utility macros to construct all the masks for a depth/swap
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* combination. The 's' parameter says whether the format is PNG
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* (big endian bytes) or not. Only the three odd numbered passes are
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* (big endian bytes) or not. Only the three odd-numbered passes are
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* required for the display/block algorithm.
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*/
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# define S_MASKS(d,s) { S_MASK(0,d,s), S_MASK(1,d,s), S_MASK(2,d,s),\
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@@ -2943,7 +2938,8 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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/* Hence the pre-compiled masks indexed by PACKSWAP (or not), depth and
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* then pass:
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*/
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static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] = {
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static PNG_CONST png_uint_32 row_mask[2/*PACKSWAP*/][3/*depth*/][6] =
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{
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/* Little-endian byte masks for PACKSWAP */
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{ S_MASKS(1,0), S_MASKS(2,0), S_MASKS(4,0) },
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/* Normal (big-endian byte) masks - PNG format */
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@@ -2953,7 +2949,8 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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/* display_mask has only three entries for the odd passes, so index by
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* pass>>1.
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*/
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static PNG_CONST png_uint_32 display_mask[2][3][3] = {
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static PNG_CONST png_uint_32 display_mask[2][3][3] =
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{
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/* Little-endian byte masks for PACKSWAP */
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{ B_MASKS(1,0), B_MASKS(2,0), B_MASKS(4,0) },
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/* Normal (big-endian byte) masks - PNG format */
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@@ -3129,7 +3126,7 @@ png_combine_row(png_structp png_ptr, png_bytep dp, int display)
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/* Check for double byte alignment and, if possible, use a
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* 16-bit copy. Don't attempt this for narrow images - ones that
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* are less than an interlace panel wide. Don't attempt it for
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* wide bytes-to-copy either - use the png_memcpy there.
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* wide bytes_to_copy either - use the png_memcpy there.
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*/
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if (bytes_to_copy < 16 /*else use png_memcpy*/ &&
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png_isaligned(dp, png_uint_16) &&
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@@ -3506,13 +3503,19 @@ png_read_filter_row_sub(png_row_infop row_info, png_bytep row,
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png_size_t istop = row_info->rowbytes;
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unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
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png_bytep rp = row + bpp;
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#if 0
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png_bytep lp = row;
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#endif
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PNG_UNUSED(prev_row)
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for (i = bpp; i < istop; i++)
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{
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#if 0
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*rp = (png_byte)(((int)(*rp) + (int)(*lp++)) & 0xff);
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#else
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*rp = (png_byte)(((int)(*rp) + (int)(*(rp-bpp))) & 0xff);
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#endif
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rp++;
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}
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}
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@@ -3540,7 +3543,9 @@ png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
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png_size_t i;
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png_bytep rp = row;
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png_const_bytep pp = prev_row;
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#if 0
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png_bytep lp = row;
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#endif
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unsigned int bpp = (row_info->pixel_depth + 7) >> 3;
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png_size_t istop = row_info->rowbytes - bpp;
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@@ -3555,7 +3560,11 @@ png_read_filter_row_avg(png_row_infop row_info, png_bytep row,
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for (i = 0; i < istop; i++)
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{
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*rp = (png_byte)(((int)(*rp) +
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#if 0
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(int)(*pp++ + *lp++) / 2 ) & 0xff);
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#else
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(int)(*pp++ + *(rp-bpp)) / 2 ) & 0xff);
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#endif
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rp++;
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}
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