libjxl

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pgx.cc (4339B)

      1 // Copyright (c) the JPEG XL Project Authors. All rights reserved.
      2 //
      3 // Use of this source code is governed by a BSD-style
      4 // license that can be found in the LICENSE file.
      5 
      6 #include "lib/extras/enc/pgx.h"
      7 
      8 #include <jxl/codestream_header.h>
      9 #include <string.h>
     10 
     11 #include "lib/extras/packed_image.h"
     12 #include "lib/jxl/base/byte_order.h"
     13 
     14 namespace jxl {
     15 namespace extras {
     16 namespace {
     17 
     18 constexpr size_t kMaxHeaderSize = 200;
     19 
     20 Status EncodeHeader(const JxlBasicInfo& info, char* header,
     21                     int* chars_written) {
     22   if (info.alpha_bits > 0) {
     23     return JXL_FAILURE("PGX: can't store alpha");
     24   }
     25   if (info.num_color_channels != 1) {
     26     return JXL_FAILURE("PGX: must be grayscale");
     27   }
     28   // TODO(lode): verify other bit depths: for other bit depths such as 1 or 4
     29   // bits, have a test case to verify it works correctly. For bits > 16, we may
     30   // need to change the way external_image works.
     31   if (info.bits_per_sample != 8 && info.bits_per_sample != 16) {
     32     return JXL_FAILURE("PGX: bits other than 8 or 16 not yet supported");
     33   }
     34 
     35   // Use ML (Big Endian), LM may not be well supported by all decoders.
     36   *chars_written = snprintf(header, kMaxHeaderSize, "PG ML + %u %u %u\n",
     37                             info.bits_per_sample, info.xsize, info.ysize);
     38   JXL_RETURN_IF_ERROR(static_cast<unsigned int>(*chars_written) <
     39                       kMaxHeaderSize);
     40   return true;
     41 }
     42 
     43 Status EncodeImagePGX(const PackedFrame& frame, const JxlBasicInfo& info,
     44                       std::vector<uint8_t>* bytes) {
     45   char header[kMaxHeaderSize];
     46   int header_size = 0;
     47   JXL_RETURN_IF_ERROR(EncodeHeader(info, header, &header_size));
     48 
     49   const PackedImage& color = frame.color;
     50   const JxlPixelFormat format = color.format;
     51   const uint8_t* in = reinterpret_cast<const uint8_t*>(color.pixels());
     52   size_t data_bits_per_sample = PackedImage::BitsPerChannel(format.data_type);
     53   size_t bytes_per_sample = data_bits_per_sample / kBitsPerByte;
     54   size_t num_samples = info.xsize * info.ysize;
     55 
     56   if (info.bits_per_sample != data_bits_per_sample) {
     57     return JXL_FAILURE("Bit depth does not match pixel data type");
     58   }
     59 
     60   std::vector<uint8_t> pixels(num_samples * bytes_per_sample);
     61 
     62   if (format.data_type == JXL_TYPE_UINT8) {
     63     memcpy(pixels.data(), in, num_samples * bytes_per_sample);
     64   } else if (format.data_type == JXL_TYPE_UINT16) {
     65     if (format.endianness != JXL_BIG_ENDIAN) {
     66       const uint8_t* p_in = in;
     67       uint8_t* p_out = pixels.data();
     68       for (size_t i = 0; i < num_samples; ++i, p_in += 2, p_out += 2) {
     69         StoreBE16(LoadLE16(p_in), p_out);
     70       }
     71     } else {
     72       memcpy(pixels.data(), in, num_samples * bytes_per_sample);
     73     }
     74   } else {
     75     return JXL_FAILURE("Unsupported pixel data type");
     76   }
     77 
     78   bytes->resize(static_cast<size_t>(header_size) + pixels.size());
     79   memcpy(bytes->data(), header, static_cast<size_t>(header_size));
     80   memcpy(bytes->data() + header_size, pixels.data(), pixels.size());
     81 
     82   return true;
     83 }
     84 
     85 class PGXEncoder : public Encoder {
     86  public:
     87   std::vector<JxlPixelFormat> AcceptedFormats() const override {
     88     std::vector<JxlPixelFormat> formats;
     89     for (const JxlDataType data_type : {JXL_TYPE_UINT8, JXL_TYPE_UINT16}) {
     90       for (JxlEndianness endianness : {JXL_BIG_ENDIAN, JXL_LITTLE_ENDIAN}) {
     91         formats.push_back(JxlPixelFormat{/*num_channels=*/1,
     92                                          /*data_type=*/data_type,
     93                                          /*endianness=*/endianness,
     94                                          /*align=*/0});
     95       }
     96     }
     97     return formats;
     98   }
     99   Status Encode(const PackedPixelFile& ppf, EncodedImage* encoded_image,
    100                 ThreadPool* pool) const override {
    101     JXL_RETURN_IF_ERROR(VerifyBasicInfo(ppf.info));
    102     encoded_image->icc.assign(ppf.icc.begin(), ppf.icc.end());
    103     encoded_image->bitstreams.clear();
    104     encoded_image->bitstreams.reserve(ppf.frames.size());
    105     for (const auto& frame : ppf.frames) {
    106       JXL_RETURN_IF_ERROR(VerifyPackedImage(frame.color, ppf.info));
    107       encoded_image->bitstreams.emplace_back();
    108       JXL_RETURN_IF_ERROR(
    109           EncodeImagePGX(frame, ppf.info, &encoded_image->bitstreams.back()));
    110     }
    111     return true;
    112   }
    113 };
    114 
    115 }  // namespace
    116 
    117 std::unique_ptr<Encoder> GetPGXEncoder() {
    118   return jxl::make_unique<PGXEncoder>();
    119 }
    120 
    121 }  // namespace extras
    122 }  // namespace jxl