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[libpng16] Added example programs for the new 'simplified' API.

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John Bowler 2011-11-24 08:22:24 -06:00 committed by Glenn Randers-Pehrson
parent e1bb124baa
commit 36082cffcd
6 changed files with 643 additions and 5 deletions
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7
ANNOUNCE
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@ -1,5 +1,5 @@
Libpng 1.6.0alpha01 - November 23, 2011
Libpng 1.6.0alpha01 - November 24, 2011
This is not intended to be a public release. It will be replaced
within a few weeks by a public version or by another test version.
@ -99,7 +99,7 @@ Version 1.5.7beta04 [November 17, 2011]
Also removed a duplicate setting of this flag.
Added files that were omitted from the libpng-1.5.7beta03 zip distribution.
Version 1.5.7beta05 [November 23, 2011]
Version 1.5.7beta05 [(PENDING RELEASE)]
Removed "zTXt" from warning in generic chunk decompression function.
Validate time settings passed to pngset() and png_convert_to_rfc1123()
(Frank Busse).
@ -107,7 +107,8 @@ Version 1.5.7beta05 [November 23, 2011]
Added MINGW support to CMakeLists.txt
Reject invalid compression flag or method when reading the iTXt chunk.
Version 1.6.0alpha01 [November 23, 2011]
Version 1.6.0alpha01 [November 24, 2011]
Added example programs for the new 'simplified' API.
Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
(subscription required; visit

5
CHANGES
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@ -3744,7 +3744,7 @@ Version 1.5.7beta04 [November 17, 2011]
Also removed a duplicate setting of this flag.
Added files that were omitted from the libpng-1.5.7beta03 zip distribution.
Version 1.5.7beta05 [November 23, 2011]
Version 1.5.7beta05 [(PENDING RELEASE)]
Removed "zTXt" from warning in generic chunk decompression function.
Validate time settings passed to pngset() and png_convert_to_rfc1123()
(Frank Busse).
@ -3752,7 +3752,8 @@ Version 1.5.7beta05 [November 23, 2011]
Added MINGW support to CMakeLists.txt
Reject invalid compression flag or method when reading the iTXt chunk.
Version 1.6.0alpha01 [November 23, 2011]
Version 1.6.0alpha01 [November 24, 2011]
Added example programs for the new 'simplified' API.
Send comments/corrections/commendations to png-mng-implement at lists.sf.net
(subscription required; visit

20
contrib/examples/README.txt Normal file
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This directory contains examples of libpng usage.
NO COPYRIGHT IS CLAIMED TO ANY OF THE FILES IN THIS DIRECTORY.
They have been placed in the public domain by the authors.
The files may be used freely in any way. The intention is that appropriate
parts of the files be used in other libpng-using programs without any need for
the authors of the using code to seek copyright or license from the original
authors.
The source code and comments in this directory are the original work of the
people named below. No other person or organization has made contributions to
the work in this directory.
ORIGINAL AUTHORS
The following people have contributed to the code in this directory. None
of the people below claim any rights with regard to the contents of this
directory.
John Bowler <jbowler@acm.org>

178
contrib/examples/iccfrompng.c Normal file
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/*- iccfrompng
*
* COPYRIGHT: please read the file "README.txt" from the containing directory..
* This file has been placed in the public domain by the authors.
*
* Extract any icc profiles found in the given PNG files. This is a simple
* example of a program which extracts information from the header of a PNG file
* without processing the image. Notice that some header information may occur
* after the image data, textual data and comments are an example; the approach
* in this file won't work reliably for such data because it only looks for the
* information in the section of the file that preceeds the image data.
*
* Compile and link against libpng and zlib, plus anything else required on the
* system you use.
*
* To use supply a list of PNG files containing iCCP chunks, the chunks will be
* extracted to a similarly named file with the extension replaced by 'icc',
* which will be overwritten without warning.
*/
#include <stdlib.h>
#include <setjmp.h>
#include <string.h>
#include <stdio.h>
#include <png.h>
static int verbose = 1;
static png_byte no_profile[] = "no profile";
static png_bytep
extract(FILE *fp, png_uint_32 *proflen)
{
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,0,0,0);
png_infop info_ptr = NULL;
png_bytep result = NULL;
/* Initialize for error or no profile: */
*proflen = 0;
if (png_ptr == NULL)
{
fprintf(stderr, "iccfrompng: version library mismatch?\n");
return 0;
}
if (setjmp(png_jmpbuf(png_ptr)))
{
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
return 0;
}
png_init_io(png_ptr, fp);
info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == NULL)
png_error(png_ptr, "OOM allocating info structure");
png_read_info(png_ptr, info_ptr);
{
png_charp name;
int compression_type;
png_bytep profile;
if (png_get_iCCP(png_ptr, info_ptr, &name, &compression_type, &profile,
proflen) & PNG_INFO_iCCP)
{
result = malloc(*proflen);
if (result != NULL)
memcpy(result, profile, *proflen);
else
png_error(png_ptr, "OOM allocating profile buffer");
}
else
result = no_profile;
}
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
return result;
}
static int
extract_one_file(const char *filename)
{
int result = 0;
FILE *fp = fopen(filename, "rb");
if (fp != NULL)
{
png_uint_32 proflen = 0;
png_bytep profile = extract(fp, &proflen);
if (profile != NULL && profile != no_profile)
{
size_t len;
char *output;
{
const char *ep = strrchr(filename, '.');
if (ep != NULL)
len = ep-filename;
else
len = strlen(filename);
}
output = malloc(len + 5);
if (output != NULL)
{
FILE *of;
memcpy(output, filename, len);
strcpy(output+len, ".icc");
of = fopen(output, "wb");
if (of != NULL)
{
if (fwrite(profile, proflen, 1, of) == 1 &&
fflush(of) == 0 &&
fclose(of) == 0)
{
if (verbose)
printf("%s -> %s\n", filename, output);
/* Success return */
result = 1;
}
else
{
fprintf(stderr, "%s: error writing profile\n", output);
if (remove(output))
fprintf(stderr, "%s: could not remove file\n", output);
}
}
else
fprintf(stderr, "%s: failed to open output file\n", output);
free(output);
}
else
fprintf(stderr, "%s: OOM allocating string!\n", filename);
free(profile);
}
else if (verbose && profile == no_profile)
printf("%s has no profile\n", filename);
}
else
fprintf(stderr, "%s: could not open file\n", filename);
return result;
}
int
main(int argc, char **argv)
{
int i;
int extracted = 0;
for (i=1; i<argc; ++i)
{
if (strcmp(argv[i], "-q") == 0)
verbose = 0;
else if (extract_one_file(argv[i]))
extracted = 1;
}
/* Exit code is true if any extract succeeds */
return extracted == 0;
}

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contrib/examples/pngpixel.c Normal file
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/*- pngpixel
*
* COPYRIGHT: please read the file "README.txt" from the containing directory.
* This file has been placed in the public domain by the authors.
*
* Read a single pixel value from a PNG file.
*
* This code illustrates basic 'by-row' reading of a PNG file using libpng.
* Rows are read until a particular pixel is found, the value of this pixel is
* then printed on stdou.
*
* The code illustrates how to do this on interlaced as well as non-interlaced
* images. Normally you would call png_set_interlace_handling() to have libpng
* deal with the interlace for you, but that obliges you to buffer half of the
* image to assemble the interlaced rows. In this code
* png_set_interlace_handling() is not called and, instead, the code handles the
* interlace passes directly looking for the required pixel.
*/
#include <stdlib.h>
#include <stdio.h>
#include <setjmp.h> /* required for error handling */
/* Normally use <png.h> here to get the installed libpng, but this is done to
* ensure the code picks up the local libpng implementation:
*/
#include "../../png.h"
/* Return component 'c' of pixel 'x' from the given row. */
static unsigned int
component(png_const_bytep row, png_uint_32 x, unsigned int c,
unsigned int bit_depth, unsigned int channels)
{
/* PNG images can be up to 2^31 pixels wide, but this means they can be up to
* 2^37 bits wide (for a 64-bit pixel - the largest possible) and hence 2^34
* bytes wide. Since the row fitted into memory, however, the following must
* work:
*/
png_uint_32 bit_offset_hi = bit_depth * ((x >> 6) * channels + c);
png_uint_32 bit_offset_lo = bit_depth * ((x & 0x3f) * channels + c);
row = (png_const_bytep)(((PNG_CONST png_byte (*)[8])row) + bit_offset_hi);
row += bit_offset_lo >> 3;
bit_offset_lo &= 0x07;
/* PNG pixels are packed into bytes to put the first pixel in the highest
* bits of the byte and into two bytes for 16-bit values with the high 8 bits
* first, so:
*/
switch (bit_depth)
{
case 1: return (row[0] >> (7-bit_offset_lo)) & 0x01;
case 2: return (row[0] >> (6-bit_offset_lo)) & 0x03;
case 4: return (row[0] >> (4-bit_offset_lo)) & 0x0f;
case 8: return row[0];
case 16: return (row[0] << 8) + row[1];
default:
/* This should never happen, it indicates a bug in this program or in
* libpng itself:
*/
fprintf(stderr, "pngpixel: invalid bit depth %u\n", bit_depth);
exit(1);
}
}
/* Print a pixel from a row returned by libpng; determine the row format, find
* the pixel, and print the relevant information to stdout.
*/
static void
print_pixel(png_structp png_ptr, png_infop info_ptr, png_const_bytep row,
png_uint_32 x)
{
PNG_CONST unsigned int bit_depth = png_get_bit_depth(png_ptr, info_ptr);
switch (png_get_color_type(png_ptr, info_ptr))
{
case PNG_COLOR_TYPE_GRAY:
printf("GRAY %u\n", component(row, x, 0, bit_depth, 1));
return;
/* The palette case is slightly more difficult - the palette and, if
* present, the tRNS ('transparency', though the values are really
* opacity) data must be read to give the full picture:
*/
case PNG_COLOR_TYPE_PALETTE:
{
PNG_CONST unsigned int index = component(row, x, 0, bit_depth, 1);
png_colorp palette = NULL;
int num_palette = 0;
if ((png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette) &
PNG_INFO_PLTE) && num_palette > 0 && palette != NULL)
{
png_bytep trans_alpha = NULL;
int num_trans = 0;
if ((png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans,
NULL) & PNG_INFO_tRNS) && num_trans > 0 &&
trans_alpha != NULL)
printf("INDEXED %u = %d %d %d %d\n", index,
palette[index].red, palette[index].green,
palette[index].blue,
index < num_trans ? trans_alpha[index] : 255);
else /* no transparency */
printf("INDEXED %u = %d %d %d\n", index,
palette[index].red, palette[index].green,
palette[index].blue);
}
else
printf("INDEXED %u = invalid index\n", index);
}
return;
case PNG_COLOR_TYPE_RGB:
printf("RGB %u %u %u\n", component(row, x, 0, bit_depth, 3),
component(row, x, 1, bit_depth, 3),
component(row, x, 2, bit_depth, 3));
return;
case PNG_COLOR_TYPE_GRAY_ALPHA:
printf("GRAY+ALPHA %u %u\n", component(row, x, 0, bit_depth, 2),
component(row, x, 1, bit_depth, 2));
return;
case PNG_COLOR_TYPE_RGB_ALPHA:
printf("RGBA %u %u %u %u\n", component(row, x, 0, bit_depth, 4),
component(row, x, 1, bit_depth, 4),
component(row, x, 2, bit_depth, 4),
component(row, x, 3, bit_depth, 4));
return;
default:
png_error(png_ptr, "invalid color type");
}
}
int main(int argc, const char **argv)
{
/* This program uses the default, <setjmp.h> based, libpng error handling
* mechanism, therefore any local variable that exists before the call to
* setjmp and is changed after the call to setjmp returns successfully must
* be declared with 'volatile' to ensure that their values don't get
* destroyed by longjmp:
*/
volatile int result = 1/*fail*/;
if (argc == 4)
{
long x = atol(argv[1]);
long y = atol(argv[2]);
FILE *f = fopen(argv[3], "rb");
volatile png_bytep row = NULL;
if (f != NULL)
{
/* libpng requires a callback function for handling errors; this
* callback must not return. The default callback function uses a
* stored <setjmp.h> style jmp_buf which is held in a png_struct and
* writes error messages to stderr. Creating the png_struct is a
* little tricky; just copy the following code.
*/
png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
NULL, NULL, NULL);
if (png_ptr != NULL)
{
png_infop info_ptr = png_create_info_struct(png_ptr);
if (info_ptr != NULL)
{
/* Declare stack variables to hold pointers to locally allocated
* data.
*/
/* Initialize the error control buffer: */
if (setjmp(png_jmpbuf(png_ptr)) == 0)
{
png_uint_32 width, height;
int bit_depth, color_type, interlace_method,
compression_method, filter_method;
png_bytep row_tmp;
/* Now associate the recently opened (FILE*) with the default
* libpng initialization functions. Sometimes libpng is
* compiled without stdio support (it can be difficult to do
* in some environments); in that case you will have to write
* your own read callback to read data from the (FILE*).
*/
png_init_io(png_ptr, f);
/* And read the first part of the PNG file - the header and
* all the information up to the first pixel.
*/
png_read_info(png_ptr, info_ptr);
/* This fills in enough information to tell us the width of
* each row in bytes, allocate the appropriate amount of
* space. In this case png_malloc is used - it will not
* return if memory isn't available.
*/
row = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
info_ptr));
/* To avoid the overhead of using a volatile auto copy row_tmp
* to a local here - just use row for the png_free below.
*/
row_tmp = row;
/* All the information we need is in the header is returned by
* png_get_IHDR, if this fails we can now use 'png_error' to
* signal the error and return control to the setjmp above.
*/
if (png_get_IHDR(png_ptr, info_ptr, &width, &height,
&bit_depth, &color_type, &interlace_method,
&compression_method, &filter_method))
{
int passes, pass;
/* png_set_interlace_handling returns the number of
* passes required as well as turning on libpng's
* handling, but since we do it ourselves this is
* necessary:
*/
switch (interlace_method)
{
case PNG_INTERLACE_NONE:
passes = 1;
break;
case PNG_INTERLACE_ADAM7:
passes = PNG_INTERLACE_ADAM7_PASSES;
break;
default:
png_error(png_ptr, "pngpixel: unknown interlace");
}
/* Now read the pixels, pass-by-pass, row-by-row: */
png_start_read_image(png_ptr);
for (pass=0; pass<passes; ++pass)
{
png_uint_32 ystart, xstart, ystep, xstep;
png_uint_32 py;
if (interlace_method == PNG_INTERLACE_ADAM7)
{
/* Sometimes the whole pass is empty because the
* image is too narrow or too short. libpng
* expects to be called for each row that is
* present in the pass, so it may be necessary to
* skip the loop below (over py) if the image is
* too narrow.
*/
if (PNG_PASS_COLS(width, pass) == 0)
continue;
/* We need the starting pixel and the offset
* between each pixel in this pass; use the macros
* in png.h:
*/
xstart = PNG_PASS_START_COL(pass);
ystart = PNG_PASS_START_ROW(pass);
xstep = PNG_PASS_COL_OFFSET(pass);
ystep = PNG_PASS_ROW_OFFSET(pass);
}
else
{
ystart = xstart = 0;
ystep = xstep = 1;
}
/* To find the pixel loop over 'py' for each pass
* reading a row and then checking to see if it
* contains the pixel.
*/
for (py = ystart; py < height; py += ystep)
{
png_uint_32 px, ppx;
/* png_read_row takes two pointers. When libpng
* handles the interlace the first is filled in
* pixel-by-pixel, the second receives the same
* pixels but they are replicated across the
* unwritten pixels so far for each pass. When we
* do the interlace, however, they just contain
* the pixels from the interlace pass - giving
* both is wasteful and pointless.
*/
png_read_row(png_ptr, row_tmp, NULL);
/* Now find the pixel if it is in this row; there
* are, of course, much better ways of doing this
* than using a for loop:
*/
if (y == py) for (px = xstart, ppx = 0;
px < width; px += xstep, ++ppx) if (x == px)
{
/* 'ppx' is the index of the pixel in the row
* buffer.
*/
print_pixel(png_ptr, info_ptr, row_tmp, ppx);
/* Now terminate the loops early - we have
* found and handled the required data.
*/
goto pass_loop_end;
} /* x loop */
} /* y loop */
} /* pass loop */
/* Finally free the temporary buffer: */
pass_loop_end:
row = NULL;
png_free(png_ptr, row_tmp);
}
else
png_error(png_ptr, "pngpixel: png_get_IHDR failed");
}
else
{
/* Else libpng has raised an error. An error message has
* already been output, it is only necessary to clean up
* locally allocated data:
*/
if (row != NULL)
{
/* The default implementation of png_free never errors out
* (it just crashes if something goes wrong), but the safe
* way of using it is still to clear 'row' before calling
* png_free:
*/
png_bytep row_tmp = row;
row = NULL;
png_free(png_ptr, row_tmp);
}
}
png_destroy_info_struct(png_ptr, &info_ptr);
}
else
fprintf(stderr, "pngpixel: out of memory allocating png_info\n");
png_destroy_read_struct(&png_ptr, NULL, NULL);
}
else
fprintf(stderr, "pngpixel: out of memory allocating png_struct\n");
}
else
fprintf(stderr, "pngpixel: %s: could not open file\n", argv[3]);
}
else
/* Wrong number of arguments */
fprintf(stderr, "pngpixel: usage: pngpixel x y png-file\n");
return result;
}

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contrib/examples/pngtopng.c Normal file
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/*- pngtopng
*
* COPYRIGHT: please read the file "README.txt" from the containing directory.
* This file has been placed in the public domain by the authors.
*
* Read a PNG and write it out in a fixed format
*
* This sample code is just the code from the top of 'example.c' with some error
* handling added. See example.c for more comments.
*/
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
/* Normally use <png.h> here to get the installed libpng, but this is done to
* ensure the code picks up the local libpng implementation:
*/
#include "../../png.h"
int main(int argc, const char **argv)
{
int result = 1;
if (argc == 3)
{
png_image image;
memset(&image, 0, sizeof image);
if (png_image_begin_read_from_file(&image, argv[1]))
{
png_bytep buffer;
/* Change this to try different formats! */
image.format = PNG_FORMAT_RGBA;
buffer = malloc(PNG_IMAGE_SIZE(image));
if (buffer != NULL)
{
if (png_image_finish_read(&image, NULL/*background*/, buffer,
0/*row_stride*/))
{
if (png_image_write_to_file(&image, argv[2],
0/*convert_to_8bit*/, buffer, 0/*row_stride*/))
result = 0;
else
fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
image.message);
}
else
fprintf(stderr, "pngtopng: read %s: %s\n", argv[1], image.message);
}
else
fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
(unsigned long)PNG_IMAGE_SIZE(image));
}
else
/* Failed to read the first argument: */
fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
}
else
/* Wrong number of arguments */
fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
return result;
}