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// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "lib/extras/dec/pgx.h"
#include <string.h>
#include "lib/jxl/base/bits.h"
#include "lib/jxl/base/compiler_specific.h"
namespace jxl {
namespace extras {
namespace {
struct HeaderPGX {
// NOTE: PGX is always grayscale
size_t xsize;
size_t ysize;
size_t bits_per_sample;
bool big_endian;
bool is_signed;
};
class Parser {
public:
explicit Parser(const Span<const uint8_t> bytes)
: pos_(bytes.data()), end_(pos_ + bytes.size()) {}
// Sets "pos" to the first non-header byte/pixel on success.
Status ParseHeader(HeaderPGX* header, const uint8_t** pos) {
// codec.cc ensures we have at least two bytes => no range check here.
if (pos_[0] != 'P' || pos_[1] != 'G') return false;
pos_ += 2;
return ParseHeaderPGX(header, pos);
}
// Exposed for testing
Status ParseUnsigned(size_t* number) {
if (pos_ == end_) return JXL_FAILURE("PGX: reached end before number");
if (!IsDigit(*pos_)) return JXL_FAILURE("PGX: expected unsigned number");
*number = 0;
while (pos_ < end_ && *pos_ >= '0' && *pos_ <= '9') {
*number *= 10;
*number += *pos_ - '0';
++pos_;
}
return true;
}
private:
static bool IsDigit(const uint8_t c) { return '0' <= c && c <= '9'; }
static bool IsLineBreak(const uint8_t c) { return c == '\r' || c == '\n'; }
static bool IsWhitespace(const uint8_t c) {
return IsLineBreak(c) || c == '\t' || c == ' ';
}
Status SkipSpace() {
if (pos_ == end_) return JXL_FAILURE("PGX: reached end before space");
const uint8_t c = *pos_;
if (c != ' ') return JXL_FAILURE("PGX: expected space");
++pos_;
return true;
}
Status SkipLineBreak() {
if (pos_ == end_) return JXL_FAILURE("PGX: reached end before line break");
// Line break can be either "\n" (0a) or "\r\n" (0d 0a).
if (*pos_ == '\n') {
pos_++;
return true;
} else if (*pos_ == '\r' && pos_ + 1 != end_ && *(pos_ + 1) == '\n') {
pos_ += 2;
return true;
}
return JXL_FAILURE("PGX: expected line break");
}
Status SkipSingleWhitespace() {
if (pos_ == end_) return JXL_FAILURE("PGX: reached end before whitespace");
if (!IsWhitespace(*pos_)) return JXL_FAILURE("PGX: expected whitespace");
++pos_;
return true;
}
Status ParseHeaderPGX(HeaderPGX* header, const uint8_t** pos) {
JXL_RETURN_IF_ERROR(SkipSpace());
if (pos_ + 2 > end_) return JXL_FAILURE("PGX: header too small");
if (*pos_ == 'M' && *(pos_ + 1) == 'L') {
header->big_endian = true;
} else if (*pos_ == 'L' && *(pos_ + 1) == 'M') {
header->big_endian = false;
} else {
return JXL_FAILURE("PGX: invalid endianness");
}
pos_ += 2;
JXL_RETURN_IF_ERROR(SkipSpace());
if (pos_ == end_) return JXL_FAILURE("PGX: header too small");
if (*pos_ == '+') {
header->is_signed = false;
} else if (*pos_ == '-') {
header->is_signed = true;
} else {
return JXL_FAILURE("PGX: invalid signedness");
}
pos_++;
// Skip optional space
if (pos_ < end_ && *pos_ == ' ') pos_++;
JXL_RETURN_IF_ERROR(ParseUnsigned(&header->bits_per_sample));
JXL_RETURN_IF_ERROR(SkipSingleWhitespace());
JXL_RETURN_IF_ERROR(ParseUnsigned(&header->xsize));
JXL_RETURN_IF_ERROR(SkipSingleWhitespace());
JXL_RETURN_IF_ERROR(ParseUnsigned(&header->ysize));
// 0xa, or 0xd 0xa.
JXL_RETURN_IF_ERROR(SkipLineBreak());
// TODO(jon): could do up to 24-bit by converting the values to
// JXL_TYPE_FLOAT.
if (header->bits_per_sample > 16) {
return JXL_FAILURE("PGX: >16 bits not yet supported");
}
// TODO(lode): support signed integers. This may require changing the way
// external_image works.
if (header->is_signed) {
return JXL_FAILURE("PGX: signed not yet supported");
}
size_t numpixels = header->xsize * header->ysize;
size_t bytes_per_pixel = header->bits_per_sample <= 8 ? 1 : 2;
if (pos_ + numpixels * bytes_per_pixel > end_) {
return JXL_FAILURE("PGX: data too small");
}
*pos = pos_;
return true;
}
const uint8_t* pos_;
const uint8_t* const end_;
};
} // namespace
Status DecodeImagePGX(const Span<const uint8_t> bytes,
const ColorHints& color_hints,
const SizeConstraints& constraints,
PackedPixelFile* ppf) {
Parser parser(bytes);
HeaderPGX header = {};
const uint8_t* pos;
if (!parser.ParseHeader(&header, &pos)) return false;
JXL_RETURN_IF_ERROR(
VerifyDimensions(&constraints, header.xsize, header.ysize));
if (header.bits_per_sample == 0 || header.bits_per_sample > 32) {
return JXL_FAILURE("PGX: bits_per_sample invalid");
}
JXL_RETURN_IF_ERROR(ApplyColorHints(color_hints, /*color_already_set=*/false,
/*is_gray=*/true, ppf));
ppf->info.xsize = header.xsize;
ppf->info.ysize = header.ysize;
// Original data is uint, so exponent_bits_per_sample = 0.
ppf->info.bits_per_sample = header.bits_per_sample;
ppf->info.exponent_bits_per_sample = 0;
ppf->info.uses_original_profile = true;
// No alpha in PGX
ppf->info.alpha_bits = 0;
ppf->info.alpha_exponent_bits = 0;
ppf->info.num_color_channels = 1; // Always grayscale
ppf->info.orientation = JXL_ORIENT_IDENTITY;
JxlDataType data_type;
if (header.bits_per_sample > 8) {
data_type = JXL_TYPE_UINT16;
} else {
data_type = JXL_TYPE_UINT8;
}
const JxlPixelFormat format{
/*num_channels=*/1,
/*data_type=*/data_type,
/*endianness=*/header.big_endian ? JXL_BIG_ENDIAN : JXL_LITTLE_ENDIAN,
/*align=*/0,
};
ppf->frames.clear();
// Allocates the frame buffer.
ppf->frames.emplace_back(header.xsize, header.ysize, format);
const auto& frame = ppf->frames.back();
size_t pgx_remaining_size = bytes.data() + bytes.size() - pos;
if (pgx_remaining_size < frame.color.pixels_size) {
return JXL_FAILURE("PGX file too small");
}
memcpy(frame.color.pixels(), pos, frame.color.pixels_size);
return true;
}
} // namespace extras
} // namespace jxl
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