From cde307896307f3009f78462212dc6cda8d99cd52 Mon Sep 17 00:00:00 2001 From: John Bowler Date: Sat, 2 May 2015 19:53:40 -0500 Subject: [PATCH] [libpng16] Added contrib/examples/simpleover.c, to demonstrate how to handle alpha compositing of multiple images, using the "simplified API" --- ANNOUNCE | 7 +- CHANGES | 5 +- contrib/examples/simpleover.c | 642 ++++++++++++++++++++++++++++++++++ 3 files changed, 651 insertions(+), 3 deletions(-) create mode 100644 contrib/examples/simpleover.c diff --git a/ANNOUNCE b/ANNOUNCE index 4d8fe9241..463cf7fa3 100644 --- a/ANNOUNCE +++ b/ANNOUNCE @@ -1,4 +1,4 @@ -Libpng 1.6.18beta03 - April 29, 2015 +Libpng 1.6.18beta03 - May 3, 2015 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. @@ -38,9 +38,12 @@ Version 1.6.18beta02 [April 26, 2015] Suppressed some warnings from the Borland C++ 5.5.1/5.82 compiler (Bug report by Viktor Szaka'ts). -Version 1.6.18beta03 [April 29, 2015] +Version 1.6.18beta03 [May 3, 2015] Replaced "unexpected" with an integer (0xabadca11) in pngset.c where a long was expected, to avoid a compiler warning when PNG_DEBUG > 1. + Added contrib/examples/simpleover.c, to demonstrate how to handle + alpha compositing of multiple images, using the "simplified API" + (John Bowler). Send comments/corrections/commendations to png-mng-implement at lists.sf.net (subscription required; visit diff --git a/CHANGES b/CHANGES index 35c9d43f2..49963a07f 100644 --- a/CHANGES +++ b/CHANGES @@ -5218,9 +5218,12 @@ Version 1.6.18beta02 [April 26, 2015] Suppressed some warnings from the Borland C++ 5.5.1/5.82 compiler (Bug report by Viktor Szaka'ts). -Version 1.6.18beta03 [April 29, 2015] +Version 1.6.18beta03 [May 3, 2015] Replaced "unexpected" with an integer (0xabadca11) in pngset.c where a long was expected, to avoid a compiler warning when PNG_DEBUG > 1. + Added contrib/examples/simpleover.c, to demonstrate how to handle + alpha compositing of multiple images, using the "simplified API" + (John Bowler). Send comments/corrections/commendations to png-mng-implement at lists.sf.net (subscription required; visit diff --git a/contrib/examples/simpleover.c b/contrib/examples/simpleover.c new file mode 100644 index 000000000..bd0382951 --- /dev/null +++ b/contrib/examples/simpleover.c @@ -0,0 +1,642 @@ +/*- simpleover + * + * COPYRIGHT: Written by John Cunningham Bowler, 2015. + * To the extent possible under law, the author has waived all copyright and + * related or neighboring rights to this work. This work is published from: + * 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. + * + * Finally read an output (background) PNG using the 24-bit RGB format (the + * PNG will be composited on green (0x00ff00) by default if it has an alpha + * channel) and apply the intermediate image generated above to specified + * locations in the image. + * + * The command line has the general format: + * + * simpleover [output.png] + * {--sprite=width,height,name {[--at=x,y] {sprite.png}}} + * {--add=name {x,y}} + * + * The --sprite and --add options may occur multiple times, they are executed + * in order. --add may refer to any sprite already read. + * + * This code is intended to show how to composite multiple images together + * 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. + */ +#include +#include +#include +#include +#include + +/* Normally use here to get the installed libpng, but this is done to + * ensure the code picks up the local libpng implementation, so long as this + * file is linked against a sufficiently recent libpng (1.6+) it is ok to + * change this to : + */ +#include "../../png.h" + +#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]; +}; + +#if 0 /* div by 65535 test program */ +#include +#include + +int main(void) { + double err = 0; + unsigned int xerr = 0; + unsigned int r = 32768; + { + unsigned int x = 0; + + 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; + } + + 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); + } + + printf("error %f @ %u\n", err, xerr); + + return 0; +} +#endif /* div by 65535 test program */ + +static void +sprite_op(const struct sprite *sprite, int x_offset, int y_offset, + 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 + * image processing operation could be used here. + */ + + + /* Check for an x or y offset that pushes 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)) + { + unsigned int y = 0; + + if (y_offset < 0) + y = -y_offset; /* Skip to first visible row */ + + do + { + unsigned int x = 0; + + if (x_offset < 0) + x = -x_offset; + + do + { + /* In and out are RGBA values, so: */ + 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 + * input alpha is 0 the output is not changed. + */ + if (in_alpha > 0) + { + png_uint_16 *out_pixel = sprite->buffer + + ((y+y_offset) * sprite->width + (x+x_offset))*4; + + /* This is the weight to apply to the output: */ + in_alpha = 65535-in_alpha; + + if (in_alpha > 0) + { + /* The input must be composed onto the output. This means + * multiplying the current output pixel value by the inverse + * of the input alpha (1-alpha). A division is required but + * it is by the constant 65535. Approximate this as: + * + * (x + (x >> 16) + (x >> 31) + 32768) >> 16; + * + * This is exact (and does not overflow) for all values of + * x in the range 0..65535*65535. (Note that the calculation + * produces the closest integer, the maximum error is <0.5). + */ + png_uint_32 tmp; + +# define compose(c)\ + tmp = out_pixel[c] * in_alpha;\ + tmp = (tmp + (tmp >> 16) + (tmp >> 31) + 32768) >> 16;\ + out_pixel[c] = tmp + in_pixel[c] + + /* The following is very vectorizable... */ + compose(0); + compose(1); + compose(2); + compose(3); + } + + else + 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); + } +} + +static int +create_sprite(struct sprite *sprite, int *argc, const char ***argv) +{ + /* Read the arguments and create this sprite, the sprite buffer has already + * been allocated. This reads the input PNGs one by one in linear format, + * composes them onto the sprite buffer (the code in the function above) + * then saves the result, converting it on the fly to PNG RGBA 8-bit format. + */ + while (*argc > 0) + { + char tombstone; + int x = 0, y = 0; + + if ((*argv)[0][0] == '-' && (*argv)[0][1] == '-') + { + /* The only supported option is --at. */ + if (sscanf((*argv)[0], "--at=%d,%d%c", &x, &y, &tombstone) != 2) + break; /* success; caller will parse this option */ + + ++*argv, --*argc; + } + + else + { + /* The argument has to be a file name */ + png_image image; + + image.version = PNG_IMAGE_VERSION; + + if (png_image_begin_read_from_file(&image, (*argv)[0])) + { + png_uint_16p buffer; + + image.format = PNG_FORMAT_LINEAR_RGB_ALPHA; + + buffer = malloc(PNG_IMAGE_SIZE(image)); + + if (buffer != NULL) + { + if (png_image_finish_read(&image, NULL/*background*/, buffer, + 0/*row_stride*/, + NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP*/)) + { + /* This is the place were the Porter-Duff 'Over' operator + * needs to be done by this code. In fact any image + * processing required can be done here; the data is in + * the correct format (linear, 16-bit) and source and + * destination are in memory. + */ + sprite_op(sprite, x, y, &image, buffer); + free(buffer); + ++*argv, --*argc; + /* And continue to the next argument */ + continue; + } + + else + { + free(buffer); + fprintf(stderr, "simpleover: read %s: %s\n", (*argv)[0], + image.message); + } + } + + else + { + fprintf(stderr, "simpleover: out of memory: %lu bytes\n", + (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 + * are detected in the Simplified API it cleans up itself. + */ + png_image_free(&image); + } + } + + else + { + /* Failed to read the first argument: */ + fprintf(stderr, "simpleover: %s: %s\n", (*argv)[0], image.message); + } + + return 0; /* failure */ + } + } + + /* All the sprite operations have completed successfully, save the RGBA + * buffer as a PNG using the simplified write API. + */ + sprite->file = tmpfile(); + + if (sprite->file != NULL) + { + png_image save; + + memset(&save, 0, sizeof save); + save.version = PNG_IMAGE_VERSION; + save.opaque = NULL; + save.width = sprite->width; + save.height = sprite->height; + save.format = PNG_FORMAT_LINEAR_RGB_ALPHA; + 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*/)) + { + /* Success, the buffer is no longer needed: */ + free(sprite->buffer); + sprite->buffer = NULL; + return 1; /* ok */ + } + + else + fprintf(stderr, "simpleover: write sprite %s: %s\n", sprite->name, + save.message); + } + + else + 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) +{ + /* Given a --add argument naming this sprite perform the operations listed + * in the following arguments. The arguments are expected to have the form + * (x,y), which is just an offset at which to add the sprite to the + * output. + */ + while (*argc > 0) + { + char tombstone; + int x, y; + + if ((*argv)[0][0] == '-' && (*argv)[0][1] == '-') + return 1; /* success */ + + if (sscanf((*argv)[0], "%d,%d%c", &x, &y, &tombstone) == 2) + { + /* Now add the new image into the sprite data, but only if it + * 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) + { + fprintf(stderr, "simpleover: sprite %s @ (%d,%d) outside image\n", + sprite->name, x, y); + /* Could just skip this, but for the moment it is an error */ + return 0; /* error */ + } + + else + { + /* Since we know the sprite fits we can just read it into the + * output using the simplified API. + */ + png_image in; + + in.version = PNG_IMAGE_VERSION; + rewind(sprite->file); + + if (png_image_begin_read_from_stdio(&in, sprite->file)) + { + 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*/)) + { + ++*argv, --*argc; + continue; + } + } + + /* The read failed: */ + fprintf(stderr, "simpleover: add sprite %s: %s\n", sprite->name, + in.message); + return 0; /* error */ + } + } + + else + { + fprintf(stderr, "simpleover: --add='%s': invalid position %s\n", + sprite->name, (*argv)[0]); + return 0; /* error */ + } + } + + return 1; /* ok */ +} + +static int +simpleover_process(png_imagep output, png_bytep out_buf, int argc, + const char **argv) +{ + int result = 1; /* success */ +# define csprites 10/*limit*/ +# define str(a) #a + int nsprites = 0; + struct sprite sprites[csprites]; + + while (argc > 0) + { + result = 0; /* fail */ + + if (strncmp(argv[0], "--sprite=", 9) == 0) + { + char tombstone; + + if (nsprites < csprites) + { + int n; + + 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); + + if ((n == 2 || n == 3) && + 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); + + /* Allocate a buffer for the sprite, calculate the buffer + * size: + */ + buf_size = sizeof (png_uint_16 [4]); + buf_size *= sprites[nsprites].width; + buf_size *= sprites[nsprites].height; + + /* This can overflow a (size_t), check for this: */ + tmp = buf_size; + tmp /= sprites[nsprites].width; + tmp /= sprites[nsprites].height; + + if (tmp == sizeof (png_uint_16 [4])) + { + sprites[nsprites].buffer = malloc(buf_size); + /* This buffer must be initialized to transparent: */ + memset(sprites[nsprites].buffer, 0, buf_size); + + if (sprites[nsprites].buffer != NULL) + { + sprites[nsprites].file = NULL; + ++argv, --argc; + + if (create_sprite(sprites+nsprites++, &argc, &argv)) + { + result = 1; /* still ok */ + continue; + } + + break; /* error */ + } + } + + /* Overflow, or OOM */ + fprintf(stderr, "simpleover: %s: sprite too large\n", argv[0]); + break; + } + + else + { + fprintf(stderr, "simpleover: %s: invalid sprite (%u,%u)\n", + argv[0], sprites[nsprites].width, sprites[nsprites].height); + break; + } + } + + else + { + fprintf(stderr, "simpleover: %s: too many sprites\n", argv[0]); + break; + } + } + + else if (strncmp(argv[0], "--add=", 6) == 0) + { + const char *name = argv[0]+6; + int isprite = nsprites; + + ++argv, --argc; + + while (--isprite >= 0) + { + if (strcmp(sprites[isprite].name, name) == 0) + { + if (!add_sprite(output, out_buf, sprites+isprite, &argc, &argv)) + goto out; /* error in addspite */ + + break; + } + } + + if (isprite < 0) /* sprite not found */ + { + fprintf(stderr, "simpleover: --add='%s': sprite not found\n", name); + break; + } + } + + else + { + fprintf(stderr, "simpleover: %s: unrecognized operation\n", argv[0]); + break; + } + + result = 1; /* ok */ + } + + /* Clean up the cache of sprites: */ +out: + while (--nsprites >= 0) + { + if (sprites[nsprites].buffer != NULL) + free(sprites[nsprites].buffer); + + if (sprites[nsprites].file != NULL) + (void)fclose(sprites[nsprites].file); + } + + return result; +} + +int main(int argc, const char **argv) +{ + int result = 1; /* default to fail */ + + if (argc >= 2) + { + int argi = 2; + const char *output = NULL; + png_image image; + + if (argc > 2 && argv[2][0] != '-'/*an operation*/) + { + output = argv[2]; + argi = 3; + } + + image.version = PNG_IMAGE_VERSION; + if (png_image_begin_read_from_file(&image, argv[1])) + { + png_bytep buffer; + + image.format = PNG_FORMAT_RGB; /* 24-bit RGB */ + + buffer = malloc(PNG_IMAGE_SIZE(image)); + + if (buffer != NULL) + { + png_color background = {0, 0xff, 0}; /* green (aka "lime") */ + + if (png_image_finish_read(&image, &background, buffer, + 0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */)) + { + /* At this point png_image_finish_read has cleaned up the + * allocated data in png_image, and only the buffer needs to be + * freed. + * + * Perform the remaining operations: + */ + 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*/)) || + (output == NULL && + 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); + } + + /* else simpleover_process writes an error message */ + } + + else + fprintf(stderr, "simpleover: read %s: %s\n", argv[1], + image.message); + + free(buffer); + } + + else + { + fprintf(stderr, "simpleover: out of memory: %lu bytes\n", + (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 + * complete the read because of running out of memory. + */ + png_image_free(&image); + } + } + + else + { + /* Failed to read the first argument: */ + fprintf(stderr, "simpleover: %s: %s\n", argv[1], image.message); + } + } + + else + { + /* Usage message */ + 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" + " on green.\n" + "\n" + " Optionally, before output, process additional PNG files:\n" + "\n" + " --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" + " 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" + " offset (x,y) in the output image. Each sprite must fit\n" + " completely within the output image.\n" + "\n" + " PNG files are processed in the order they occur on the command\n" + " line and thus the first PNG processed appears as the bottommost\n" + " in the output image.\n"); + } + + return result; +}