Add a tool to find hot pixels
It works well for my Nikon. Note that hot pixels can be eliminated in the camera itself, when you run sensor cleaning immediately after a very long exposure of darkness.
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A0420B94F92B9493
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@ -192,7 +192,7 @@ if get_option('tools').enabled()
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cc.find_library('jq'), dependency('libpng'), dependency('libraw')]
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tools_c_args = cc.get_supported_arguments(
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'-Wno-unused-function', '-Wno-unused-parameter')
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foreach tool : ['info', 'pnginfo', 'rawinfo']
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foreach tool : ['info', 'pnginfo', 'rawinfo', 'hotpixels']
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executable(tool, 'tools/' + tool + '.c', tiff_tables,
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dependencies : tools_dependencies,
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c_args: tools_c_args)
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@ -0,0 +1,210 @@
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//
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// hotpixels.c: look for hot pixels in raw image files
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//
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// Usage: pass a bunch of raw photo images taken with the lens cap on at,
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// e.g., ISO 8000-12800 @ 1/20-1/60, and store the resulting file as,
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// e.g., Nikon D7500.badpixels, which can then be directly used by Rawtherapee.
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//
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// Copyright (c) 2023, Přemysl Eric Janouch <p@janouch.name>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted.
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//
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// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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//
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#include <libraw.h>
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#if LIBRAW_VERSION < LIBRAW_MAKE_VERSION(0, 21, 0)
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#error LibRaw 0.21.0 or newer is required.
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#endif
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#include <errno.h>
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#include <stdbool.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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static void *
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xreallocarray(void *o, size_t n, size_t m)
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{
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if (m && n > SIZE_MAX / m) {
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fprintf(stderr, "xreallocarray: %s\n", strerror(ENOMEM));
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exit(EXIT_FAILURE);
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}
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void *p = realloc(o, n * m);
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if (!p && n && m) {
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fprintf(stderr, "xreallocarray: %s\n", strerror(errno));
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exit(EXIT_FAILURE);
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}
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return p;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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struct coord { ushort x, y; };
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static bool
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coord_equals(struct coord a, struct coord b)
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{
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return a.x == b.x && a.y == b.y;
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}
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static int
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coord_cmp(const void *a, const void *b)
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{
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const struct coord *ca = (const struct coord *) a;
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const struct coord *cb = (const struct coord *) b;
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return ca->y != cb->y
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? (int) ca->y - (int) cb->y
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: (int) ca->x - (int) cb->x;
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}
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struct candidates {
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struct coord *xy;
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size_t len;
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size_t alloc;
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};
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static void
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candidates_add(struct candidates *c, ushort x, ushort y)
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{
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if (c->len == c->alloc) {
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c->alloc += 64;
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c->xy = xreallocarray(c->xy, sizeof *c->xy, c->alloc);
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}
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c->xy[c->len++] = (struct coord) {x, y};
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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// A stretch of zeroes that is assumed to mean start of outliers.
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#define SPAN 10
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static const char *
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process_raw(struct candidates *c, const uint8_t *p, size_t len)
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{
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libraw_data_t *iprc = libraw_init(LIBRAW_OPIONS_NO_DATAERR_CALLBACK);
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if (!iprc)
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return "failed to obtain a LibRaw handle";
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int err = 0;
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if ((err = libraw_open_buffer(iprc, p, len)) ||
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(err = libraw_unpack(iprc))) {
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libraw_close(iprc);
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return libraw_strerror(err);
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}
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if (!iprc->rawdata.raw_image) {
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libraw_close(iprc);
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return "only Bayer raws are supported, not Foveon";
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}
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// Make a histogram.
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uint64_t bins[USHRT_MAX] = {};
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for (ushort yy = 0; yy < iprc->sizes.height; yy++) {
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for (ushort xx = 0; xx < iprc->sizes.width; xx++) {
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ushort y = iprc->sizes.top_margin + yy;
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ushort x = iprc->sizes.left_margin + xx;
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bins[iprc->rawdata.raw_image[y * iprc->sizes.raw_width + x]]++;
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}
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}
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// Detecting outliers is not completely straight-forward,
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// it may help to see the histogram.
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if (getenv("HOTPIXELS_HISTOGRAM")) {
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for (ushort i = 0; i < USHRT_MAX; i++)
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fprintf(stderr, "%u ", (unsigned) bins[i]);
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fputc('\n', stderr);
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}
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// Go to the first non-zero pixel value.
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size_t last = 0;
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for (; last < USHRT_MAX; last++)
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if (bins[last])
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break;
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// Find the last pixel value we assume to not be hot.
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for (; last < USHRT_MAX - SPAN - 1; last++) {
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uint64_t nonzero = 0;
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for (int i = 1; i <= SPAN; i++)
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nonzero += bins[last + i];
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if (!nonzero)
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break;
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}
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// Store coordinates for all pixels above that value.
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for (ushort yy = 0; yy < iprc->sizes.height; yy++) {
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for (ushort xx = 0; xx < iprc->sizes.width; xx++) {
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ushort y = iprc->sizes.top_margin + yy;
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ushort x = iprc->sizes.left_margin + xx;
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if (iprc->rawdata.raw_image[y * iprc->sizes.raw_width + x] > last)
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candidates_add(c, xx, yy);
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}
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}
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libraw_close(iprc);
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return NULL;
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}
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// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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static const char *
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do_file(struct candidates *c, const char *filename)
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{
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FILE *fp = fopen(filename, "rb");
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if (!fp)
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return strerror(errno);
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uint8_t *data = NULL, buf[256 << 10];
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size_t n, len = 0;
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while ((n = fread(buf, sizeof *buf, sizeof buf / sizeof *buf, fp))) {
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data = xreallocarray(data, len + n, 1);
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memcpy(data + len, buf, n);
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len += n;
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}
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const char *err = ferror(fp)
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? strerror(errno)
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: process_raw(c, data, len);
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fclose(fp);
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free(data);
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return err;
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}
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int
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main(int argc, char *argv[])
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{
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struct candidates c = {};
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for (int i = 1; i < argc; i++) {
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const char *filename = argv[i], *err = do_file(&c, filename);
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if (err) {
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fprintf(stderr, "%s: %s\n", filename, err);
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return EXIT_FAILURE;
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}
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}
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qsort(c.xy, c.len, sizeof *c.xy, coord_cmp);
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// If it is detected in all passed photos, it is probably indeed bad.
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int count = 1;
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for (size_t i = 1; i <= c.len; i++) {
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if (i != c.len && coord_equals(c.xy[i - 1], c.xy[i])) {
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count++;
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continue;
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}
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if (count == argc - 1)
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printf("%u %u\n", c.xy[i - 1].x, c.xy[i - 1].y);
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count = 1;
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}
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return 0;
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}
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