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examples: Refactor and reformat using clang-format

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Add contrib/examples/.clang-format, tailored to fit the existing code
as closely as possible. The end goal is to set up automatic formatting
for the entire libpng source tree. We're doing this experiment in this
subdirectory, for now.

Also make refactoring changes, as follows:

 * Rewrite the preprocessor checks `#if PNG_FOO_SUPPORTED` to stop
   compilation immediately, with a descriptive `#error` about what
   needs to be supported.

 * Rewrite and reflow comments, add braces and brackets, and make other
   minor modifications that are suited for the clang-format'ed code.
This commit is contained in:
Cosmin Truta
2025-06-01 22:40:38 +03:00
parent 197bbfe0d5
commit 3bca02e274
5 changed files with 366 additions and 189 deletions
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232
contrib/examples/simpleover.c
View File

@@ -6,9 +6,9 @@
* United States.
*
* Read several PNG files, which should have an alpha channel or transparency
* information, and composite them together to produce one or more 16-bit linear
* RGBA intermediates. This involves doing the correct 'over' composition to
* combine the alpha channels and corresponding data.
* information, and composite them together to produce one or more 16-bit
* linear RGBA intermediates. This involves doing the 'over' compositing
* operation to combine the alpha channels and corresponding data.
*
* Finally read an output (background) PNG using the 24-bit RGB format (the
* PNG will be composited on green (#00ff00) by default if it has an alpha
@@ -28,8 +28,8 @@
* correctly. Apart from the libpng Simplified API the only work done in here
* is to combine multiple input PNG images into a single sprite; this involves
* a Porter-Duff 'over' operation and the input PNG images may, as a result,
* be regarded as being layered one on top of the other with the first (leftmost
* on the command line) being at the bottom and the last on the top.
* be regarded as being layered one on top of the other with the first
* (leftmost on the command line) being at the bottom and the last on the top.
*/
#include <stddef.h>
#include <stdlib.h>
@@ -44,54 +44,61 @@
*/
#include "../../png.h"
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
#if !defined(PNG_SIMPLIFIED_READ_SUPPORTED)
#error This program requires libpng supporting the simplified read API
#endif
#define sprite_name_chars 15
struct sprite {
FILE *file;
png_uint_16p buffer;
unsigned int width;
unsigned int height;
char name[sprite_name_chars+1];
struct sprite
{
FILE *file;
png_uint_16p buffer;
unsigned int width;
unsigned int height;
char name[sprite_name_chars + 1];
};
#if 0 /* div by 65535 test program */
#include <math.h>
#include <stdio.h>
int main(void) {
int
main(void)
{
double err = 0;
unsigned int xerr = 0;
unsigned int r = 32769;
unsigned int x = 0;
do
{
unsigned int x = 0;
unsigned int t = x + (x >> 16) /*+ (x >> 31)*/ + r;
double v = x, errtest;
do {
unsigned int t = x + (x >> 16) /*+ (x >> 31)*/ + r;
double v = x, errtest;
if (t < x)
{
fprintf(stderr, "overflow: %u+%u -> %u\n", x, r, t);
return 1;
}
if (t < x) {
fprintf(stderr, "overflow: %u+%u -> %u\n", x, r, t);
return 1;
v /= 65535;
errtest = v;
t >>= 16;
errtest -= t;
if (errtest > err)
{
err = errtest;
xerr = x;
if (errtest >= .5)
{
fprintf(stderr, "error: %u/65535 = %f, not %u, error %f\n",
x, v, t, errtest);
return 0;
}
v /= 65535;
errtest = v;
t >>= 16;
errtest -= t;
if (errtest > err) {
err = errtest;
xerr = x;
if (errtest >= .5) {
fprintf(stderr, "error: %u/65535 = %f, not %u, error %f\n",
x, v, t, errtest);
return 0;
}
}
} while (++x <= 65535U*65535U);
}
}
} while (++x <= 65535U * 65535U);
printf("error %f @ %u\n", err, xerr);
@@ -101,7 +108,7 @@ int main(void) {
static void
sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
png_imagep image, const png_uint_16 *buffer)
png_imagep image, const png_uint_16 *buffer)
{
/* This is where the Porter-Duff 'Over' operator is evaluated; change this
* code to change the operator (this could be parameterized). Any other
@@ -112,8 +119,8 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
/* Check for an x or y offset that pushes any part of the image beyond the
* right or bottom of the sprite:
*/
if ((y_offset < 0 || (unsigned)/*SAFE*/y_offset < sprite->height) &&
(x_offset < 0 || (unsigned)/*SAFE*/x_offset < sprite->width))
if ((y_offset < 0 || /*SAFE*/ (unsigned)y_offset < sprite->height) &&
(x_offset < 0 || /*SAFE*/ (unsigned)x_offset < sprite->width))
{
unsigned int y = 0;
@@ -130,7 +137,7 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
do
{
/* In and out are RGBA values, so: */
const png_uint_16 *in_pixel = buffer + (y * image->width + x)*4;
const png_uint_16 *in_pixel = buffer + (y * image->width + x) * 4;
png_uint_32 in_alpha = in_pixel[3];
/* This is the optimized Porter-Duff 'Over' operation, when the
@@ -139,10 +146,10 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
if (in_alpha > 0)
{
png_uint_16 *out_pixel = sprite->buffer +
((y+y_offset) * sprite->width + (x+x_offset))*4;
((y + y_offset) * sprite->width + (x + x_offset)) * 4;
/* This is the weight to apply to the output: */
in_alpha = 65535-in_alpha;
in_alpha = 65535 - in_alpha;
if (in_alpha > 0)
{
@@ -159,9 +166,9 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
*/
png_uint_32 tmp;
# define compose(c)\
tmp = out_pixel[c] * in_alpha;\
tmp = (tmp + (tmp >> 16) + 32769) >> 16;\
# define compose(c) \
tmp = out_pixel[c] * in_alpha; \
tmp = (tmp + (tmp >> 16) + 32769) >> 16; \
out_pixel[c] = tmp + in_pixel[c]
/* The following is very vectorizable... */
@@ -172,15 +179,15 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
}
else
out_pixel[0] = in_pixel[0],
out_pixel[1] = in_pixel[1],
out_pixel[2] = in_pixel[2],
{
out_pixel[0] = in_pixel[0];
out_pixel[1] = in_pixel[1];
out_pixel[2] = in_pixel[2];
out_pixel[3] = in_pixel[3];
}
}
}
while (++x < image->width);
}
while (++y < image->height);
} while (++x < image->width);
} while (++y < image->height);
}
}
@@ -224,9 +231,8 @@ create_sprite(struct sprite *sprite, int *argc, const char ***argv)
if (buffer != NULL)
{
if (png_image_finish_read(&image, NULL/*background*/, buffer,
0/*row_stride*/,
NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP*/))
if (png_image_finish_read(&image, NULL /*background*/, buffer,
0 /*row_stride*/, NULL /*colormap*/))
{
/* This is the place where the Porter-Duff 'Over' operator
* needs to be done by this code. In fact, any image
@@ -245,14 +251,14 @@ create_sprite(struct sprite *sprite, int *argc, const char ***argv)
{
free(buffer);
fprintf(stderr, "simpleover: read %s: %s\n", (*argv)[0],
image.message);
image.message);
}
}
else
{
fprintf(stderr, "simpleover: out of memory: %lu bytes\n",
(unsigned long)PNG_IMAGE_SIZE(image));
(unsigned long)PNG_IMAGE_SIZE(image));
/* png_image_free must be called if we abort the Simplified API
* read because of a problem detected in this code. If problems
@@ -290,8 +296,9 @@ create_sprite(struct sprite *sprite, int *argc, const char ***argv)
save.flags = PNG_IMAGE_FLAG_FAST;
save.colormap_entries = 0;
if (png_image_write_to_stdio(&save, sprite->file, 1/*convert_to_8_bit*/,
sprite->buffer, 0/*row_stride*/, NULL/*colormap*/))
if (png_image_write_to_stdio(&save, sprite->file, 1 /*convert_to_8_bit*/,
sprite->buffer, 0 /*row_stride*/,
NULL /*colormap*/))
{
/* Success; the buffer is no longer needed: */
free(sprite->buffer);
@@ -301,19 +308,20 @@ create_sprite(struct sprite *sprite, int *argc, const char ***argv)
else
fprintf(stderr, "simpleover: write sprite %s: %s\n", sprite->name,
save.message);
save.message);
}
else
fprintf(stderr, "simpleover: sprite %s: could not allocate tmpfile: %s\n",
sprite->name, strerror(errno));
fprintf(stderr,
"simpleover: sprite %s: could not allocate tmpfile: %s\n",
sprite->name, strerror(errno));
return 0; /* fail */
}
static int
add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
int *argc, const char ***argv)
int *argc, const char ***argv)
{
/* Given a --add argument naming this sprite, perform the operations listed
* in the following arguments. The arguments are expected to have the form
@@ -334,13 +342,13 @@ add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
* will fit.
*/
if (x < 0 || y < 0 ||
(unsigned)/*SAFE*/x >= output->width ||
(unsigned)/*SAFE*/y >= output->height ||
sprite->width > output->width-x ||
sprite->height > output->height-y)
/*SAFE*/ (unsigned)x >= output->width ||
/*SAFE*/ (unsigned)y >= output->height ||
sprite->width > output->width - x ||
sprite->height > output->height - y)
{
fprintf(stderr, "simpleover: sprite %s @ (%d,%d) outside image\n",
sprite->name, x, y);
sprite->name, x, y);
/* Could just skip this, but for the moment it is an error */
return 0; /* error */
}
@@ -359,10 +367,10 @@ add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
{
in.format = PNG_FORMAT_RGB; /* force compose */
if (png_image_finish_read(&in, NULL/*background*/,
out_buf + (y*output->width + x)*3/*RGB*/,
output->width*3/*row_stride*/,
NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP*/))
if (png_image_finish_read(
&in, NULL /*background*/,
out_buf + (y * output->width + x) * 3 /*RGB*/,
output->width * 3 /*row_stride*/, NULL /*colormap*/))
{
++*argv, --*argc;
continue;
@@ -371,7 +379,7 @@ add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
/* The read failed: */
fprintf(stderr, "simpleover: add sprite %s: %s\n", sprite->name,
in.message);
in.message);
return 0; /* error */
}
}
@@ -379,7 +387,7 @@ add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
else
{
fprintf(stderr, "simpleover: --add='%s': invalid position %s\n",
sprite->name, (*argv)[0]);
sprite->name, (*argv)[0]);
return 0; /* error */
}
}
@@ -389,10 +397,10 @@ add_sprite(png_imagep output, png_bytep out_buf, struct sprite *sprite,
static int
simpleover_process(png_imagep output, png_bytep out_buf, int argc,
const char **argv)
const char **argv)
{
int result = 1; /* success */
# define csprites 10/*limit*/
# define csprites 10 /*limit*/
# define str(a) #a
int nsprites = 0;
struct sprite sprites[csprites];
@@ -412,23 +420,25 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
sprites[nsprites].width = sprites[nsprites].height = 0;
sprites[nsprites].name[0] = 0;
n = sscanf(argv[0], "--sprite=%u,%u,%" str(sprite_name_chars) "s%c",
&sprites[nsprites].width, &sprites[nsprites].height,
sprites[nsprites].name, &tombstone);
n = sscanf(argv[0],
"--sprite=%u,%u,%" str(sprite_name_chars) "s%c",
&sprites[nsprites].width, &sprites[nsprites].height,
sprites[nsprites].name, &tombstone);
if ((n == 2 || n == 3) &&
sprites[nsprites].width > 0 && sprites[nsprites].height > 0)
(sprites[nsprites].width > 0) &&
(sprites[nsprites].height > 0))
{
size_t buf_size, tmp;
/* Default a name if not given. */
if (sprites[nsprites].name[0] == 0)
sprintf(sprites[nsprites].name, "sprite-%d", nsprites+1);
sprintf(sprites[nsprites].name, "sprite-%d", nsprites + 1);
/* Allocate a buffer for the sprite and calculate the buffer
* size:
*/
buf_size = sizeof (png_uint_16 [4]);
buf_size = sizeof(png_uint_16[4]);
buf_size *= sprites[nsprites].width;
buf_size *= sprites[nsprites].height;
@@ -437,7 +447,7 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
tmp /= sprites[nsprites].width;
tmp /= sprites[nsprites].height;
if (tmp == sizeof (png_uint_16 [4]))
if (tmp == sizeof(png_uint_16[4]))
{
sprites[nsprites].buffer = malloc(buf_size);
/* This buffer must be initialized to transparent: */
@@ -448,7 +458,7 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
sprites[nsprites].file = NULL;
++argv, --argc;
if (create_sprite(sprites+nsprites++, &argc, &argv))
if (create_sprite(sprites + nsprites++, &argc, &argv))
{
result = 1; /* still ok */
continue;
@@ -466,7 +476,8 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
else
{
fprintf(stderr, "simpleover: %s: invalid sprite (%u,%u)\n",
argv[0], sprites[nsprites].width, sprites[nsprites].height);
argv[0],
sprites[nsprites].width, sprites[nsprites].height);
break;
}
}
@@ -480,7 +491,7 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
else if (strncmp(argv[0], "--add=", 6) == 0)
{
const char *name = argv[0]+6;
const char *name = argv[0] + 6;
int isprite = nsprites;
++argv, --argc;
@@ -489,7 +500,8 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
{
if (strcmp(sprites[isprite].name, name) == 0)
{
if (!add_sprite(output, out_buf, sprites+isprite, &argc, &argv))
if (!add_sprite(output, out_buf, sprites + isprite,
&argc, &argv))
goto out; /* error in add_sprite */
break;
@@ -498,7 +510,8 @@ simpleover_process(png_imagep output, png_bytep out_buf, int argc,
if (isprite < 0) /* sprite not found */
{
fprintf(stderr, "simpleover: --add='%s': sprite not found\n", name);
fprintf(stderr, "simpleover: --add='%s': sprite not found\n",
name);
break;
}
}
@@ -526,7 +539,8 @@ out:
return result;
}
int main(int argc, const char **argv)
int
main(int argc, const char **argv)
{
int result = 1; /* default to fail */
@@ -536,7 +550,7 @@ int main(int argc, const char **argv)
const char *output = NULL;
png_image image;
if (argc > 2 && argv[2][0] != '-'/*an operation*/)
if (argc > 2 && argv[2][0] != '-' /*an operation*/)
{
output = argv[2];
argi = 3;
@@ -558,7 +572,7 @@ int main(int argc, const char **argv)
png_color background = {0, 0xff, 0}; /* fully saturated green */
if (png_image_finish_read(&image, &background, buffer,
0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
0 /*row_stride*/, NULL /*colormap*/))
{
/* At this point png_image_finish_read has cleaned up the
* allocated data in png_image, and only the buffer needs to be
@@ -566,22 +580,24 @@ int main(int argc, const char **argv)
*
* Perform the remaining operations:
*/
if (simpleover_process(&image, buffer, argc-argi, argv+argi))
if (simpleover_process(&image, buffer,
argc - argi, argv + argi))
{
/* Write the output: */
if ((output != NULL &&
png_image_write_to_file(&image, output,
0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
NULL/*colormap*/)) ||
png_image_write_to_file(
&image, output, 0 /*convert_to_8bit*/, buffer,
0 /*row_stride*/, NULL /*colormap*/)) ||
(output == NULL &&
png_image_write_to_stdio(&image, stdout,
0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
NULL/*colormap*/)))
png_image_write_to_stdio(
&image, stdout, 0 /*convert_to_8bit*/, buffer,
0 /*row_stride*/, NULL /*colormap*/)))
result = 0;
else
fprintf(stderr, "simpleover: write %s: %s\n",
output == NULL ? "stdout" : output, image.message);
output == NULL ? "stdout" : output,
image.message);
}
/* else simpleover_process writes an error message */
@@ -589,7 +605,7 @@ int main(int argc, const char **argv)
else
fprintf(stderr, "simpleover: read %s: %s\n", argv[1],
image.message);
image.message);
free(buffer);
}
@@ -597,7 +613,7 @@ int main(int argc, const char **argv)
else
{
fprintf(stderr, "simpleover: out of memory: %lu bytes\n",
(unsigned long)PNG_IMAGE_SIZE(image));
(unsigned long)PNG_IMAGE_SIZE(image));
/* This is the only place where a 'free' is required; libpng does
* the cleanup on error and success, but in this case we couldn't
@@ -617,7 +633,8 @@ int main(int argc, const char **argv)
else
{
/* Usage message */
fprintf(stderr,
fprintf(
stderr,
"simpleover: usage: simpleover background.png [output.png]\n"
" Output 'background.png' as a 24-bit RGB PNG file in 'output.png'\n"
" or, if not given, stdout. 'background.png' will be composited\n"
@@ -628,13 +645,13 @@ int main(int argc, const char **argv)
" --sprite=width,height,name {[--at=x,y] {sprite.png}}\n"
" Produce a transparent sprite of size (width,height) and with\n"
" name 'name'.\n"
" For each sprite.png composite it using a Porter-Duff 'Over'\n"
" operation at offset (x,y) in the sprite (defaulting to (0,0)).\n"
" For each sprite.png composite it is using a Porter-Duff 'Over'\n"
" operation at offset (x,y) in the sprite, defaulting to (0,0).\n"
" Input PNGs will be truncated to the area of the sprite.\n"
"\n"
" --add='name' {x,y}\n"
" Optionally, before output, composite a sprite, 'name', which\n"
" must have been previously produced using --sprite, at each\n"
" must have been previously produced using --sprite at each\n"
" offset (x,y) in the output image. Each sprite must fit\n"
" completely within the output image.\n"
"\n"
@@ -645,4 +662,3 @@ int main(int argc, const char **argv)
return result;
}
#endif /* SIMPLIFIED_READ */