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//
// jpeginfo.c: acquire information about JPEG files in JSON format
//
// Copyright (c) 2021, Přemysl Eric Janouch <p@janouch.name>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
#include <jv.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <stdarg.h>
// --- Utilities ---------------------------------------------------------------
static uint32_t
u32be(const uint8_t *p)
{
return (uint32_t) p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
}
static uint16_t
u16be(const uint8_t *p)
{
return (uint16_t) p[0] << 8 | p[1];
}
static uint32_t
u32le(const uint8_t *p)
{
return (uint32_t) p[3] << 24 | p[2] << 16 | p[1] << 8 | p[0];
}
static uint16_t
u16le(const uint8_t *p)
{
return (uint16_t) p[1] << 8 | p[0];
}
// --- TIFF --------------------------------------------------------------------
// TIFF Revision 6.0
// https://www.adobe.io/content/dam/udp/en/open/standards/tiff/TIFF6.pdf
//
// TIFF Technical Note 1: TIFF Trees
// https://download.osgeo.org/libtiff/old/TTN1.ps
//
// Adobe PageMaker 6.0 TIFF Technical Notes [includes TTN1]
// https://www.adobe.io/content/dam/udp/en/open/standards/tiff/TIFFPM6.pdf
//
// Exif Version 2.3
// https://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf
//
// libtiff is a mess, and the format is not particularly complicated.
// Exif libraries are senselessly copylefted.
static struct un {
uint32_t (*u32) (const uint8_t *);
uint16_t (*u16) (const uint8_t *);
} unbe = {u32be, u16be}, unle = {u32le, u16le};
struct tiffer {
struct un *un;
const uint8_t *begin, *p, *end;
uint16_t remaining_fields;
};
static bool
tiffer_u32(struct tiffer *self, uint32_t *u)
{
if (self->p + 4 > self->end)
return false;
*u = self->un->u32(self->p);
self->p += 4;
return true;
}
static bool
tiffer_u16(struct tiffer *self, uint16_t *u)
{
if (self->p + 2 > self->end)
return false;
*u = self->un->u16(self->p);
self->p += 2;
return true;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
tiffer_init(struct tiffer *self, const uint8_t *tiff, size_t len)
{
self->un = NULL;
self->begin = self->p = tiff;
self->end = tiff + len;
self->remaining_fields = 0;
const uint8_t
le[4] = {'I', 'I', 42, 0},
be[4] = {'M', 'M', 0, 42};
if (tiff + 8 > self->end)
return false;
else if (!memcmp(tiff, le, sizeof le))
self->un = &unle;
else if (!memcmp(tiff, be, sizeof be))
self->un = &unbe;
else
return false;
self->p = tiff + 4;
// The first IFD needs to be read by caller explicitly.
return true;
}
/// Read the next IFD in a sequence.
static bool
tiffer_next_ifd(struct tiffer *self)
{
// All fields from any previous IFD need to be read first.
if (self->remaining_fields)
return false;
uint32_t ifd_offset = 0;
if (!tiffer_u32(self, &ifd_offset))
return false;
// There is nothing more to read, this chain has terminated.
if (!ifd_offset)
return false;
self->p = self->begin + ifd_offset;
return tiffer_u16(self, &self->remaining_fields);
}
/// Initialize a derived TIFF reader for a subIFD at the given location.
static bool
tiffer_subifd(struct tiffer *self, uint32_t offset, struct tiffer *subreader)
{
*subreader = *self;
subreader->p = subreader->begin + offset;
return tiffer_u16(subreader, &subreader->remaining_fields);
}
enum tiffer_type {
BYTE = 1, ASCII, SHORT, LONG, RATIONAL,
SBYTE, UNDEFINED, SSHORT, SLONG, SRATIONAL, FLOAT, DOUBLE,
IFD // This last type from TIFF Technical Note 1 isn't really used much.
};
static size_t
tiffer_value_size(enum tiffer_type type)
{
switch (type) {
case BYTE:
case SBYTE:
case ASCII:
case UNDEFINED:
return 1;
case SHORT:
case SSHORT:
return 2;
case LONG:
case SLONG:
case FLOAT:
case IFD:
return 4;
case RATIONAL:
case SRATIONAL:
case DOUBLE:
return 8;
default:
return 0;
}
}
/// A lean iterator for values within entries.
struct tiffer_entry {
uint16_t tag;
enum tiffer_type type;
// For {S,}BYTE, ASCII, UNDEFINED, use these fields directly.
const uint8_t *p;
uint32_t remaining_count;
};
static bool
tiffer_next_value(struct tiffer_entry *entry)
{
if (!entry->remaining_count)
return false;
entry->p += tiffer_value_size(entry->type);
entry->remaining_count--;
return true;
}
static bool
tiffer_integer(
const struct tiffer *self, const struct tiffer_entry *entry, int64_t *out)
{
if (!entry->remaining_count)
return false;
// Somewhat excessively lenient, intended for display.
switch (entry->type) {
case BYTE:
case ASCII:
case UNDEFINED:
*out = *entry->p;
return true;
case SBYTE:
*out = (int8_t) *entry->p;
return true;
case SHORT:
*out = self->un->u16(entry->p);
return true;
case SSHORT:
*out = (int16_t) self->un->u16(entry->p);
return true;
case LONG:
case IFD:
*out = self->un->u32(entry->p);
return true;
case SLONG:
*out = (int32_t) self->un->u32(entry->p);
return true;
default:
return false;
}
}
static bool
tiffer_rational(const struct tiffer *self, const struct tiffer_entry *entry,
int64_t *numerator, int64_t *denominator)
{
if (!entry->remaining_count)
return false;
// Somewhat excessively lenient, intended for display.
switch (entry->type) {
case RATIONAL:
*numerator = self->un->u32(entry->p);
*denominator = self->un->u32(entry->p + 4);
return true;
case SRATIONAL:
*numerator = (int32_t) self->un->u32(entry->p);
*denominator = (int32_t) self->un->u32(entry->p + 4);
return true;
default:
if (!tiffer_integer(self, entry, numerator))
return false;
*denominator = 1;
return true;
}
}
static bool
tiffer_real(
const struct tiffer *self, const struct tiffer_entry *entry, double *out)
{
if (!entry->remaining_count)
return false;
// Somewhat excessively lenient, intended for display.
switch (entry->type) {
int64_t integer;
case RATIONAL:
*out = self->un->u32(entry->p) / (double) self->un->u32(entry->p + 4);
return true;
case SRATIONAL:
*out = (int32_t) self->un->u32(entry->p) /
(double) (int32_t) self->un->u32(entry->p + 4);
return true;
case FLOAT:
*out = *(float *) entry->p;
return true;
case DOUBLE:
*out = *(double *) entry->p;
return true;
default:
if (!tiffer_integer(self, entry, &integer))
return false;
*out = integer;
return true;
}
}
static bool
tiffer_next_entry(struct tiffer *self, struct tiffer_entry *entry)
{
if (!self->remaining_fields)
return false;
uint16_t type = entry->type = 0xFFFF;
if (!tiffer_u16(self, &entry->tag) || !tiffer_u16(self, &type) ||
!tiffer_u32(self, &entry->remaining_count))
return false;
// Short values may and will be inlined, rather than pointed to.
size_t values_size = tiffer_value_size(type) * entry->remaining_count;
uint32_t offset = 0;
if (values_size <= sizeof offset) {
entry->p = self->p;
self->p += sizeof offset;
} else if (tiffer_u32(self, &offset)) {
entry->p = self->begin + offset;
} else {
return false;
}
// All entries are pre-checked not to overflow.
if (entry->p + values_size > self->end)
return false;
// Setting it at the end may provide an indication while debugging.
entry->type = type;
self->remaining_fields--;
return true;
}
// --- TIFF/Exif/MPF/* tags ----------------------------------------------------
struct tiff_value {
const char *name;
uint16_t value;
};
struct tiff_entry {
const char *name;
uint16_t tag;
struct tiff_value *values;
};
static struct tiff_entry tiff_entries[] = {
{"NewSubfileType", 254, NULL},
{"SubfileType", 255, (struct tiff_value[]) {
{"Full-resolution image data", 1},
{"Reduced-resolution image data", 2},
{"Page of a multi-page image", 3},
{}
}},
{"ImageWidth", 256, NULL},
{"ImageLength", 257, NULL},
{"BitsPerSample", 258, NULL},
{"Compression", 259, (struct tiff_value[]) {
{"Uncompressed", 1},
{"CCITT 1D", 2},
{"Group 3 Fax", 3},
{"Group 4 Fax", 4},
{"LZW", 5},
{"JPEG", 6},
{"PackBits", 32773},
{}
}},
{"PhotometricInterpretation", 262, (struct tiff_value[]) {
{"WhiteIsZero", 0},
{"BlackIsZero", 1},
{"RGB", 2},
{"RGB Palette", 3},
{"Transparency mask", 4},
{"CMYK", 5},
{"YCbCr", 6},
{"CIELab", 8},
{"ICC CIELab", 9}, // Adobe PageMaker 6.0 TIFF Technical Notes
{}
}},
{"Threshholding", 263, (struct tiff_value[]) {
{"No dithering or halftoning", 1},
{"Ordered dither or halftoning", 2},
{"Randomized process", 3},
{}
}},
{"CellWidth", 264, NULL},
{"CellLength", 265, NULL},
{"FillOrder", 266, (struct tiff_value[]) {
{"MSB-first", 1},
{"LSB-first", 2},
{}
}},
{"DocumentName", 269, NULL},
{"ImageDescription", 270, NULL},
{"Make", 271, NULL},
{"Model", 272, NULL},
{"StripOffsets", 273, NULL},
{"Orientation", 274, (struct tiff_value[]) {
{"TopLeft", 1},
{"TopRight", 2},
{"BottomRight", 3},
{"BottomLeft", 4},
{"LeftTop", 5},
{"RightTop", 6},
{"RightBottom", 7},
{"LeftBottom", 8},
{}
}},
{"SamplesPerPixel", 277, NULL},
{"RowsPerStrip", 278, NULL},
{"StripByteCounts", 279, NULL},
{"MinSampleValue", 280, NULL},
{"MaxSampleValue", 281, NULL},
{"XResolution", 282, NULL},
{"YResolution", 283, NULL},
{"PlanarConfiguration", 284, (struct tiff_value[]) {
{"Chunky", 1},
{"Planar", 2},
{}
}},
{"PageName", 285, NULL},
{"XPosition", 286, NULL},
{"YPosition", 287, NULL},
{"FreeOffsets", 288, NULL},
{"FreeByteCounts", 289, NULL},
{"GrayResponseUnit", 290, (struct tiff_value[]) {
{"1/10", 1},
{"1/100", 2},
{"1/1000", 3},
{"1/10000", 4},
{"1/100000", 5},
{}
}},
{"GrayResponseCurve", 291, NULL},
{"T4Options", 292, NULL},
{"T6Options", 293, NULL},
{"ResolutionUnit", 296, (struct tiff_value[]) {
{"None", 1},
{"Inch", 2},
{"Centimeter", 3},
{}
}},
{"PageNumber", 297, NULL},
{"TransferFunction", 301, NULL},
{"Software", 305, NULL},
{"DateTime", 306, NULL},
{"Artist", 315, NULL},
{"HostComputer", 316, NULL},
{"Predictor", 317, (struct tiff_value[]) {
{"None", 1},
{"Horizontal", 2},
{}
}},
{"WhitePoint", 318, NULL},
{"PrimaryChromaticities", 319, NULL},
{"ColorMap", 320, NULL},
{"HalftoneHints", 321, NULL},
{"TileWidth", 322, NULL},
{"TileLength", 323, NULL},
{"TileOffsets", 324, NULL},
{"TileByteCounts", 325, NULL},
{"SubIFDs", 330, NULL}, // TIFF Technical Note 1: TIFF Trees
{"InkSet", 332, (struct tiff_value[]) {
{"CMYK", 1},
{"Non-CMYK", 2},
{}
}},
{"InkNames", 333, NULL},
{"NumberOfInks", 334, NULL},
{"DotRange", 336, NULL},
{"TargetPrinter", 337, NULL},
{"ExtraSamples", 338, (struct tiff_value[]) {
{"Unspecified", 0},
{"Associated alpha", 1},
{"Unassociated alpha", 2},
{}
}},
{"SampleFormat", 339, (struct tiff_value[]) {
{"Unsigned integer", 1},
{"Two's complement signed integer", 2},
{"IEEE floating-point", 3},
{"Undefined", 4},
{}
}},
{"SMinSampleValue", 340, NULL},
{"SMaxSampleValue", 341, NULL},
{"TransferRange", 342, NULL},
{"ClipPath", 343, NULL}, // TIFF Technical Note 2: Clipping Path
{"XClipPathUnits", 344, NULL}, // TIFF Technical Note 2: Clipping Path
{"YClipPathUnits", 345, NULL}, // TIFF Technical Note 2: Clipping Path
{"Indexed", 346, NULL}, // TIFF Technical Note 3: Indexed Images
{"OPIProxy", 351, NULL}, // Adobe PageMaker 6.0 TIFF Technical Notes
{"JPEGProc", 512, (struct tiff_value[]) {
{"Baseline sequential", 1},
{"Lossless Huffman", 14},
{}
}},
{"JPEGInterchangeFormat", 513, NULL},
{"JPEGInterchangeFormatLength", 514, NULL},
{"JPEGRestartInterval", 515, NULL},
{"JPEGLosslessPredictors", 517, (struct tiff_value[]) {
{"A", 1},
{"B", 2},
{"C", 3},
{"A+B+C", 4},
{"A+((B-C)/2)", 5},
{"B+((A-C)/2)", 6},
{"(A+B)/2", 7},
{}
}},
{"JPEGPointTransforms", 518, NULL},
{"JPEGQTables", 519, NULL},
{"JPEGDCTables", 520, NULL},
{"JPEGACTables", 521, NULL},
{"YCbCrCoefficients", 529, NULL},
{"YCbCrSubSampling", 530, NULL},
{"YCbCrPositioning", 531, (struct tiff_value[]) {
{"Centered", 1},
{"Cosited", 2},
{}
}},
{"ReferenceBlackWhite", 532, NULL},
{"ImageID", 32781, NULL}, // Adobe PageMaker 6.0 TIFF Technical Notes
{"Copyright", 33432, NULL},
{}
};
// TODO(p): Insert tags and values from other documentation,
// so far only tags and non-bit-field values from TIFF 6.0 and PM6 are present.
// --- Analysis ----------------------------------------------------------------
static jv
add_to_subarray(jv o, const char *key, jv value)
{
// Invalid values are not allocated, and we use up any valid one.
// Beware that jv_get() returns jv_null() rather than jv_invalid().
// Also, the header comment is lying, jv_is_valid() doesn't unreference.
jv a = jv_object_get(jv_copy(o), jv_string(key));
return jv_set(o, jv_string(key),
jv_is_valid(a) ? jv_array_append(a, value) : JV_ARRAY(value));
}
static jv
add_warning(jv o, const char *message)
{
return add_to_subarray(o, "warnings", jv_string(message));
}
static jv
add_error(jv o, const char *message)
{
return jv_object_set(o, jv_string("error"), jv_string(message));
}
// --- Exif --------------------------------------------------------------------
static jv parse_exif_ifd(struct tiffer *T);
static jv
parse_exif_subifds(struct tiffer *T, const struct tiffer_entry *entry)
{
int64_t offset = 0;
struct tiffer subT = {};
if (!tiffer_integer(T, entry, &offset) ||
offset < 0 || offset > UINT32_MAX || !tiffer_subifd(T, offset, &subT))
return jv_null();
// The chain should correspond to the values in the entry,
// we are not going to verify it.
jv a = jv_array();
do a = jv_array_append(a, parse_exif_ifd(&subT));
while (tiffer_next_ifd(&subT));
return a;
}
static jv
parse_exif_ascii(struct tiffer_entry *entry)
{
// Adobe XMP Specification Part 3: Storage in Files, 2020/1, 2.4.2
// The text may in practice contain any 8-bit encoding, but likely UTF-8.
// TODO(p): Validate UTF-8, and assume Latin 1 if unsuccessful.
jv a = jv_array();
uint8_t *nul = 0;
while ((nul = memchr(entry->p, 0, entry->remaining_count))) {
size_t len = nul - entry->p;
a = jv_array_append(a, jv_string_sized((const char *) entry->p, len));
entry->remaining_count -= len + 1;
entry->p += len + 1;
}
// Trailing NULs are required, but let's extract everything.
if (entry->remaining_count) {
a = jv_array_append(a,
jv_string_sized((const char *) entry->p, entry->remaining_count));
}
// TODO(p): May extract this into a function, and reuse it below.
if (jv_array_length(jv_copy(a)) == 1)
return jv_array_get(a, 0);
return a;
}
static jv
parse_exif_entry(jv o, struct tiffer *T, struct tiffer_entry *entry)
{
jv value = jv_true();
bool numeric = false;
double real = 0;
if (!entry->remaining_count) {
value = jv_null();
} else if (entry->type == IFD) {
value = parse_exif_subifds(T, entry);
} else if (entry->type == ASCII) {
value = parse_exif_ascii(entry);
} else if ((numeric = tiffer_real(T, entry, &real))) {
value = jv_number(real);
}
// TODO(p): Decode UNDEFINED as a hex dump, and iterate over all values.
for (const struct tiff_entry *p = tiff_entries; p->name; p++) {
if (p->tag != entry->tag)
continue;
if (numeric && p->values) {
for (const struct tiff_value *q = p->values; q->name; q++) {
if (q->value == real)
return jv_set(o, jv_string(p->name), jv_string(q->name));
}
}
return jv_set(o, jv_string(p->name), value);
}
return jv_set(o, jv_string_fmt("%u", entry->tag), value);
}
static jv
parse_exif_ifd(struct tiffer *T)
{
jv ifd = jv_object();
struct tiffer_entry entry;
while (tiffer_next_entry(T, &entry))
ifd = parse_exif_entry(ifd, T, &entry);
return ifd;
}
static jv
parse_exif(jv o, const uint8_t *p, size_t len)
{
struct tiffer T;
if (!tiffer_init(&T, p, len))
return add_warning(o, "invalid Exif");
while (tiffer_next_ifd(&T))
o = add_to_subarray(o, "TIFF", parse_exif_ifd(&T));
return o;
}
// --- ICC profiles ------------------------------------------------------------
// v2 https://www.color.org/ICC_Minor_Revision_for_Web.pdf
// v4 https://www.color.org/specification/ICC1v43_2010-12.pdf
static jv
parse_icc_mluc(jv o, const uint8_t *tag, uint32_t tag_length)
{
// v4 10.13
if (tag_length < 16)
return add_warning(o, "invalid ICC 'mluc' structure length");
uint32_t count = u32be(tag + 8);
if (count == 0)
return add_warning(o, "unnamed ICC profile");
// There is no particularly good reason for us to iterate, take the first.
const uint8_t *record = tag + 16 /* + i * u32be(tag + 12) */;
uint32_t len = u32be(&record[4]);
uint32_t off = u32be(&record[8]);
if (off + len > tag_length)
return add_warning(o, "invalid ICC 'mluc' structure record");
// Blindly assume simple ASCII, ensure NUL-termination.
char name[len], *p = name;
for (uint32_t i = 0; i < len / 2; i++)
*p++ = tag[off + i * 2 + 1];
*p++ = 0;
return jv_set(o, jv_string("ICC"),
JV_OBJECT(jv_string("name"), jv_string(name),
jv_string("version"), jv_number(4)));
}
static jv
parse_icc_desc(jv o, const uint8_t *profile, size_t profile_len,
uint32_t tag_offset, uint32_t tag_length)
{
const uint8_t *tag = profile + tag_offset;
if (tag_offset + tag_length > profile_len)
return add_warning(o, "unexpected end of ICC profile");
if (tag_length < 4)
return add_warning(o, "invalid ICC tag structure length");
// v2 6.5.17
uint32_t sig = u32be(tag);
if (sig == 0x6D6C7563 /* mluc */)
return parse_icc_mluc(o, profile + tag_offset, tag_length);
if (sig != 0x64657363 /* desc */)
return add_warning(o, "invalid ICC 'desc' structure signature");
if (tag_length < 12)
return add_warning(o, "invalid ICC 'desc' structure length");
uint32_t count = u32be(tag + 8);
if (tag_length < 12 + count)
return add_warning(o, "invalid ICC 'desc' structure length");
// Double-ensure a trailing NUL byte.
char name[count + 1];
memcpy(name, tag + 12, count);
name[count] = 0;
return jv_set(o, jv_string("ICC"),
JV_OBJECT(jv_string("name"), jv_string(name),
jv_string("version"), jv_number(2)));
}
static jv
parse_icc(jv o, const uint8_t *profile, size_t profile_len)
{
// v2 6, v4 7
if (profile_len < 132)
return add_warning(o, "ICC profile too short");
if (u32be(profile) != profile_len)
return add_warning(o, "ICC profile size mismatch");
// TODO(p): May decode more of the header fields, and validate them.
// Need to check both v2 and v4, this is all fairly annoying.
uint32_t count = u32be(profile + 128);
if (132 + count * 12 > profile_len)
return add_warning(o, "unexpected end of ICC profile");
for (uint32_t i = 0; i < count; i++) {
const uint8_t *entry = profile + 132 + i * 12;
uint32_t sig = u32be(&entry[0]);
uint32_t off = u32be(&entry[4]);
uint32_t len = u32be(&entry[8]);
// v2 6.4.32, v4 9.2.41
if (sig == 0x64657363 /* desc */)
return parse_icc_desc(o, profile, profile_len, off, len);
}
// The description is required, so this should be unreachable.
return jv_set(o, jv_string("ICC"), jv_bool(true));
}
// --- Photoshop Image Resources -----------------------------------------------
// Adobe XMP Specification Part 3: Storage in Files, 2020/1, 1.1.3 + 3.1.3
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/
static jv
process_psir(jv o, uint16_t resource_id, const char *name,
const uint8_t *data, size_t len)
{
// TODO(p): These is more to extract here. The name is most often empty.
(void) name;
(void) data;
(void) len;
return add_to_subarray(o, "PSIR", jv_number(resource_id));
}
static jv
parse_psir_block(jv o, const uint8_t *p, size_t len, size_t *advance)
{
*advance = 0;
if (len < 8 || memcmp(p, "8BIM", 4))
return add_warning(o, "bad PSIR block header");
uint16_t resource_id = u16be(p + 4);
uint8_t name_len = p[6];
const uint8_t *name = &p[7];
// Add one byte for the Pascal-ish string length prefix,
// then another one for padding to make the length even.
size_t name_len_full = (name_len + 2) & ~1U;
size_t resource_len_offset = 6 + name_len_full,
header_len = resource_len_offset + 4;
if (len < header_len)
return add_warning(o, "bad PSIR block header");
uint32_t resource_len = u32be(p + resource_len_offset);
size_t resource_len_padded = (resource_len + 1) & ~1U;
if (resource_len_padded < resource_len ||
len < header_len + resource_len_padded)
return add_warning(o, "runaway PSIR block");
char *cname = calloc(1, name_len_full);
strncpy(cname, (const char *) name, name_len);
o = process_psir(o, resource_id, cname, p + header_len, resource_len);
free(cname);
*advance = header_len + resource_len_padded;
return o;
}
static jv
parse_psir(jv o, const uint8_t *p, size_t len)
{
if (len == 0)
return add_warning(o, "empty PSIR data");
size_t advance = 0;
while (len && (o = parse_psir_block(o, p, len, &advance), advance)) {
p += advance;
len -= advance;
}
return o;
}
// --- JPEG --------------------------------------------------------------------
// Because the JPEG file format is simple, just do it manually.
// See: https://www.w3.org/Graphics/JPEG/itu-t81.pdf
enum {
TEM = 0x01,
SOF0 = 0xC0, SOF1, SOF2, SOF3,
DHT = 0xC4,
SOF5, SOF6, SOF7,
JPG = 0xC8,
SOF9, SOF10, SOF11,
DAC = 0xCC,
SOF13, SOF14, SOF15,
RST0 = 0xD0, RST1, RST2, RST3, RST4, RST5, RST6, RST7,
SOI = 0xD8,
EOI = 0xD9,
SOS = 0xDA,
DQT = 0xDB,
DNL = 0xDC,
DRI = 0xDD,
DHP = 0xDE,
EXP = 0xDF,
APP0 = 0xE0, APP1, APP2, APP3, APP4, APP5, APP6, APP7,
APP8, APP9, APP10, APP11, APP12, APP13, APP14, APP15,
JPG0 = 0xF0, JPG1, JPG2, JPG3, JPG4, JPG5, JPG6, JPG7,
JPG8, JPG9, JPG10, JPG11, JPG12, JPG13,
COM = 0xFE
};
// The rest is "RES (Reserved)", except for 0xFF (filler) and 0x00 (invalid).
static const char *marker_ids[0xFF] = {
[TEM] = "TEM",
[SOF0] = "SOF0", [SOF1] = "SOF1", [SOF2] = "SOF2", [SOF3] = "SOF3",
[DHT] = "DHT", [SOF5] = "SOF5", [SOF6] = "SOF6", [SOF7] = "SOF7",
[JPG] = "JPG", [SOF9] = "SOF9", [SOF10] = "SOF10", [SOF11] = "SOF11",
[DAC] = "DAC", [SOF13] = "SOF13", [SOF14] = "SOF14", [SOF15] = "SOF15",
[RST0] = "RST0", [RST1] = "RST1", [RST2] = "RST2", [RST3] = "RST3",
[RST4] = "RST4", [RST5] = "RST5", [RST6] = "RST6", [RST7] = "RST7",
[SOI] = "SOI", [EOI] = "EOI", [SOS] = "SOS", [DQT] = "DQT",
[DNL] = "DNL", [DRI] = "DRI", [DHP] = "DHP", [EXP] = "EXP",
[APP0] = "APP0", [APP1] = "APP1", [APP2] = "APP2", [APP3] = "APP3",
[APP4] = "APP4", [APP5] = "APP5", [APP6] = "APP6", [APP7] = "APP7",
[APP8] = "APP8", [APP9] = "APP9", [APP10] = "APP10", [APP11] = "APP11",
[APP12] = "APP12", [APP13] = "APP13", [APP14] = "APP14", [APP15] = "APP15",
[JPG0] = "JPG0", [JPG1] = "JPG1", [JPG2] = "JPG2", [JPG3] = "JPG3",
[JPG4] = "JPG4", [JPG5] = "JPG5", [JPG6] = "JPG6", [JPG7] = "JPG7",
[JPG8] = "JPG8", [JPG9] = "JPG9", [JPG10] = "JPG10", [JPG11] = "JPG11",
[JPG12] = "JPG12", [JPG13] = "JPG13", [COM] = "COM"
};
// The rest is "RES (Reserved)", except for 0xFF (filler) and 0x00 (invalid).
static const char *marker_descriptions[0xFF] = {
[TEM] = "For temporary private use in arithmetic coding",
[SOF0] = "Baseline DCT",
[SOF1] = "Extended sequential DCT",
[SOF2] = "Progressive DCT",
[SOF3] = "Lossless (sequential)",
[DHT] = "Define Huffman table(s)",
[SOF5] = "Differential sequential DCT",
[SOF6] = "Differential progressive DCT",
[SOF7] = "Differential lossless (sequential)",
[JPG] = "Reserved for JPEG extensions",
[SOF9] = "Extended sequential DCT",
[SOF10] = "Progressive DCT",
[SOF11] = "Lossless (sequential)",
[DAC] = "Define arithmetic coding conditioning(s)",
[SOF13] = "Differential sequential DCT",
[SOF14] = "Differential progressive DCT",
[SOF15] = "Differential lossless (sequential)",
[RST0] = "Restart with module 8 count 0",
[RST1] = "Restart with module 8 count 1",
[RST2] = "Restart with module 8 count 2",
[RST3] = "Restart with module 8 count 3",
[RST4] = "Restart with module 8 count 4",
[RST5] = "Restart with module 8 count 5",
[RST6] = "Restart with module 8 count 6",
[RST7] = "Restart with module 8 count 7",
[SOI] = "Start of image",
[EOI] = "End of image",
[SOS] = "Start of scan",
[DQT] = "Define quantization table(s)",
[DNL] = "Define number of lines",
[DRI] = "Define restart interval",
[DHP] = "Define hierarchical progression",
[EXP] = "Expand reference component(s)",
[APP0] = "Reserved for application segments, 0",
[APP1] = "Reserved for application segments, 1",
[APP2] = "Reserved for application segments, 2",
[APP3] = "Reserved for application segments, 3",
[APP4] = "Reserved for application segments, 4",
[APP5] = "Reserved for application segments, 5",
[APP6] = "Reserved for application segments, 6",
[APP7] = "Reserved for application segments, 7",
[APP8] = "Reserved for application segments, 8",
[APP9] = "Reserved for application segments, 9",
[APP10] = "Reserved for application segments, 10",
[APP11] = "Reserved for application segments, 11",
[APP12] = "Reserved for application segments, 12",
[APP13] = "Reserved for application segments, 13",
[APP14] = "Reserved for application segments, 14",
[APP15] = "Reserved for application segments, 15",
[JPG0] = "Reserved for JPEG extensions, 0",
[JPG1] = "Reserved for JPEG extensions, 1",
[JPG2] = "Reserved for JPEG extensions, 2",
[JPG3] = "Reserved for JPEG extensions, 3",
[JPG4] = "Reserved for JPEG extensions, 4",
[JPG5] = "Reserved for JPEG extensions, 5",
[JPG6] = "Reserved for JPEG extensions, 6",
[JPG7] = "Reserved for JPEG extensions, 7",
[JPG8] = "Reserved for JPEG extensions, 8",
[JPG9] = "Reserved for JPEG extensions, 9",
[JPG10] = "Reserved for JPEG extensions, 10",
[JPG11] = "Reserved for JPEG extensions, 11",
[JPG12] = "Reserved for JPEG extensions, 12",
[JPG13] = "Reserved for JPEG extensions, 13",
[COM] = "Comment",
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
struct data {
bool ended;
uint8_t *exif, *icc, *psir;
size_t exif_len, icc_len, psir_len;
int icc_sequence, icc_done;
};
static void
parse_append(uint8_t **buffer, size_t *buffer_len, const uint8_t *p, size_t len)
{
size_t buffer_longer = *buffer_len + len;
*buffer = realloc(*buffer, buffer_longer);
memcpy(*buffer + *buffer_len, p, len);
*buffer_len = buffer_longer;
}
static const uint8_t *
parse_marker(uint8_t marker, const uint8_t *p, const uint8_t *end,
struct data *data, jv *o)
{
// Suspected: MJPEG? Undetected format recursion, e.g., thumbnails?
// Found: Random metadata! Multi-Picture Format!
if ((data->ended = marker == EOI) && p != end)
*o = add_warning(*o, "trailing data");
// These markers stand alone, not starting a marker segment.
switch (marker) {
case RST0:
case RST1:
case RST2:
case RST3:
case RST4:
case RST5:
case RST6:
case RST7:
*o = add_warning(*o, "unexpected restart marker");
// Fall-through
case SOI:
case EOI:
case TEM:
return p;
}
uint16_t length = p[0] << 8 | p[1];
const uint8_t *payload = p + 2;
if ((p += length) > end) {
*o = add_error(*o, "runaway marker segment");
return NULL;
}
switch (marker) {
case SOF0:
case SOF1:
case SOF2:
case SOF3:
case SOF5:
case SOF6:
case SOF7:
case SOF9:
case SOF10:
case SOF11:
case SOF13:
case SOF14:
case SOF15:
case DHP: // B.2.2 and B.3.2.
// As per B.2.5, Y can be zero, then there needs to be a DNL segment.
*o = add_to_subarray(*o, "info", JV_OBJECT(
jv_string("type"), jv_string(marker_descriptions[marker]),
jv_string("bits"), jv_number(payload[0]),
jv_string("height"), jv_number(payload[1] << 8 | payload[2]),
jv_string("width"), jv_number(payload[3] << 8 | payload[4]),
jv_string("components"), jv_number(payload[5])
));
return p;
}
// See B.1.1.5, we can brute-force our way through the entropy-coded data.
if (marker == SOS) {
while (p + 2 <= end && (p[0] != 0xFF || p[1] < 0xC0 || p[1] > 0xFE ||
(p[1] >= RST0 && p[1] <= RST7)))
p++;
return p;
}
// "The interpretation is left to the application."
if (marker == COM) {
int superascii = 0;
char *buf = calloc(3, p - payload), *bufp = buf;
for (const uint8_t *q = payload; q < p; q++) {
if (*q < 128) {
*bufp++ = *q;
} else {
superascii++;
*bufp++ = 0xC0 | (*q >> 6);
*bufp++ = 0x80 | (*q & 0x3F);
}
}
*bufp++ = 0;
*o = add_to_subarray(*o, "comments", jv_string(buf));
free(buf);
if (superascii)
*o = add_warning(*o, "super-ASCII comments");
}
// These mostly contain an ASCII string header, following JPEG FIF:
//
// "Application-specific APP0 marker segments are identified
// by a zero terminated string which identifies the application
// (not 'JFIF' or 'JFXX')."
if (marker >= APP0 && marker <= APP15) {
const uint8_t *nul = memchr(payload, 0, p - payload);
int unprintable = !nul;
if (nul) {
for (const uint8_t *q = payload; q < nul; q++)
unprintable += *q < 32 || *q >= 127;
}
*o = add_to_subarray(*o, "apps",
unprintable ? jv_null() : jv_string((const char *) payload));
}
// CIPA DC-007 (Multi-Picture Format)
// http://fileformats.archiveteam.org/wiki/Multi-Picture_Format
// TODO(p): Handle by properly skipping trailing data (use MPF offsets).
// CIPA DC-006 (Stereo Still Image Format for Digital Cameras)
// http://fileformats.archiveteam.org/wiki/Multi-Picture_Format
// TODO(p): Handle by properly skipping trailing data (use Stim offsets).
// https://www.w3.org/Graphics/JPEG/jfif3.pdf
if (marker == APP0 && p - payload >= 14 && !memcmp(payload, "JFIF\0", 5)) {
payload += 5;
jv units = jv_number(payload[2]);
switch (payload[2]) {
break; case 0: units = jv_null();
break; case 1: units = jv_string("DPI");
break; case 2: units = jv_string("dots per cm");
}
// The rest is picture data.
*o = add_to_subarray(*o, "JFIF", JV_OBJECT(
jv_string("version"), jv_number(payload[0] * 100 + payload[1]),
jv_string("units"), units,
jv_string("density-x"), jv_number(payload[3] << 8 | payload[4]),
jv_string("density-y"), jv_number(payload[5] << 8 | payload[6]),
jv_string("thumbnail-w"), jv_number(payload[7]),
jv_string("thumbnail-h"), jv_number(payload[8])
));
}
if (marker == APP0 && p - payload >= 6 && !memcmp(payload, "JFXX\0", 5)) {
payload += 5;
jv extension = jv_number(payload[0]);
switch (payload[0]) {
break; case 0x10: extension = jv_string("JPEG thumbnail");
break; case 0x11: extension = jv_string("Paletted thumbnail");
break; case 0x13: extension = jv_string("RGB thumbnail");
}
// The rest is picture data.
*o = add_to_subarray(*o, "JFXX",
JV_OBJECT(jv_string("extension"), extension));
}
// https://www.cipa.jp/std/documents/e/DC-008-2012_E.pdf 4.7.2
// Adobe XMP Specification Part 3: Storage in Files, 2020/1, 1.1.3
if (marker == APP1 && p - payload >= 6 && !memcmp(payload, "Exif\0", 5)) {
payload += 6;
if (payload[-1] != 0)
*o = add_warning(*o, "weirdly padded Exif header");
if (data->exif)
*o = add_warning(*o, "multiple Exif segments");
parse_append(&data->exif, &data->exif_len, payload, p - payload);
}
// https://www.color.org/specification/ICC1v43_2010-12.pdf B.4
if (marker == APP2 && p - payload >= 14 &&
!memcmp(payload, "ICC_PROFILE\0", 12) && !data->icc_done &&
payload[12] == ++data->icc_sequence && payload[13] >= payload[12]) {
payload += 14;
parse_append(&data->icc, &data->icc_len, payload, p - payload);
data->icc_done = payload[-1] == data->icc_sequence;
}
// Adobe XMP Specification Part 3: Storage in Files, 2020/1, 1.1.3 + 3.1.3
// https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/
if (marker == APP13 && p - payload >= 14 &&
!memcmp(payload, "Photoshop 3.0\0", 14)) {
payload += 14;
parse_append(&data->psir, &data->psir_len, payload, p - payload);
}
return p;
}
static jv
parse_jpeg(jv o, const uint8_t *p, size_t len)
{
struct data data = {};
const uint8_t *end = p + len;
jv markers = jv_array();
while (p) {
// This is an expectable condition, use a simple warning.
if (p + 2 > end) {
if (!data.ended)
o = add_warning(o, "unexpected EOF");
break;
}
if (*p++ != 0xFF || *p == 0) {
o = add_error(o, "no marker found where one was expected");
break;
}
// Markers may be preceded by fill bytes.
if (*p == 0xFF) {
o = jv_object_set(o, jv_string("fillers"), jv_bool(true));
continue;
}
uint8_t marker = *p++;
markers = jv_array_append(markers,
jv_string(marker_ids[marker] ? marker_ids[marker] : "RES"));
p = parse_marker(marker, p, end, &data, &o);
}
if (data.exif) {
o = parse_exif(o, data.exif, data.exif_len);
free(data.exif);
}
if (data.icc) {
if (data.icc_done)
o = parse_icc(o, data.icc, data.icc_len);
else
o = add_warning(o, "bad ICC profile sequence");
free(data.icc);
}
if (data.psir) {
o = parse_psir(o, data.psir, data.psir_len);
free(data.psir);
}
return jv_set(o, jv_string("markers"), markers);
}
// --- I/O ---------------------------------------------------------------------
static jv
do_file(const char *filename, jv o)
{
const char *err = NULL;
FILE *fp = fopen(filename, "rb");
if (!fp) {
err = strerror(errno);
goto error;
}
uint8_t *data = NULL, buf[256 << 10];
size_t n, len = 0;
while ((n = fread(buf, sizeof *buf, sizeof buf / sizeof *buf, fp))) {
data = realloc(data, len + n);
memcpy(data + len, buf, n);
len += n;
}
if (ferror(fp)) {
err = strerror(errno);
goto error_read;
}
#if 0
// Not sure if I want to ensure their existence...
o = jv_object_set(o, jv_string("info"), jv_array());
o = jv_object_set(o, jv_string("warnings"), jv_array());
#endif
o = parse_jpeg(o, data, len);
error_read:
fclose(fp);
free(data);
error:
if (err)
o = add_error(o, err);
return o;
}
int
main(int argc, char *argv[])
{
// XXX: Can't use `xargs -P0`, there's a risk of non-atomic writes.
// Usage: find . -iname *.png -print0 | xargs -0 ./pnginfo
for (int i = 1; i < argc; i++) {
const char *filename = argv[i];
jv o = jv_object();
o = jv_object_set(o, jv_string("filename"), jv_string(filename));
o = do_file(filename, o);
jv_dumpf(o, stdout, 0 /* Might consider JV_PRINT_SORTED. */);
fputc('\n', stdout);
}
return 0;
}
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