如何在ObjectiveC/C++中打开LinearDNG？

Question

我试图在我的 MacOS 应用程序中打开 LinearDNG 文件。据我调查，CoreImage.

是不可能的

所以，问题：

是否可以使用 CoreImage 打开 LinearDNG 文件作为 16-bit/8-bit RGBA 数据？
是否可以使用 dcraw 打开 LinearDNG 文件作为 16-bit/8-bit RGBA 数据？
你知道其他库可以打开 LinearDNG 文件作为 16-bit/8-bit RGBA 数据吗？

我的 LinearDNG 文件是 16 位的。相关EXIF数据：

File Type                       : DNG
File Type Extension             : dng
MIME Type                       : image/x-adobe-dng

Bits Per Sample                 : 16 16 16
Compression                     : Uncompressed
Photometric Interpretation      : Linear Raw

Format                          : image/jpeg

我读到 CIContext 可以将图像转换为 TIFF/JPEG，但是使用这个特定 LinearDNG 文件的代码不起作用。所有 JPEG 图像都是黑色的，所有 TIFF 图像都是透明的。我想 CIImage 只是不理解这种编码。

我的测试代码：

[self convertLinearDNGToJPEG:@"super_jpeg.jpeg"];
        
[self convertLinearDNGToTIFF:kCIFormatRGBA8 fileName:@"super_kCIFormatRGBA8.tiff"];
[self convertLinearDNGToTIFF:kCIFormatRGBA16 fileName:@"super_kCIFormatRGBA16.tiff"];
[self convertLinearDNGToTIFF:kCIFormatARGB8 fileName:@"super_kCIFormatARGB8.tiff"];
[self convertLinearDNGToTIFF:kCIFormatRGBAh fileName:@"super_kCIFormatRGBAh.tiff"];

对应函数(convertLinearDNGToTIFF/convertLinearDNGToJPEG ):

- (void)convertLinearDNGToJPEG:(NSString*)fileName
{
    CIImage* inputImage = [self createInputImage];
    
    NSError* superError = nil;
    CIContext* ciContext = [self createCiContext];
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    NSURL* superURL = [NSURL fileURLWithPath: [documentsDirectory stringByAppendingPathComponent:fileName] ];
    CGColorSpaceRef superColorSpace = CGColorSpaceCreateDeviceRGB();
    [ciContext writeJPEGRepresentationOfImage:inputImage
                                        toURL:superURL
                                   colorSpace:superColorSpace
                                      options:@{} // CIImageRepresentationOption
                                        error:&superError];
}
- (void)convertLinearDNGToTIFF:(CIFormat)format fileName:(NSString*)fileName
{
    CIImage* inputImage = [self createInputImage];
    
    NSError* superError = nil;
    CIContext* ciContext = [self createCiContext];
    
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    NSURL* superURL = [NSURL fileURLWithPath: [documentsDirectory stringByAppendingPathComponent:fileName] ];
    CGColorSpaceRef superColorSpace = CGColorSpaceCreateDeviceRGB();
    [ciContext writeTIFFRepresentationOfImage:inputImage
                                        toURL:superURL
                                       format:format
                                   colorSpace:superColorSpace
                                      options:@{} // CIImageRepresentationOption
                                        error:&superError];
}

Answer 1

嗯，我试过 LibRaw：https://github.com/LibRaw/LibRaw。它能够将我的 LinearDNG 导出到 TIFF。我可以用 CoreImage 打开 TIFF。虽然白平衡是错误的。我认为这是因为 libraw 读取元数据错误（文件 samples/raw-identify.cpp）。

导出为 TIFF 的代码在文件 samples/simple_dcraw.cpp

中

/* -*- C++ -*-
 * File: simple_dcraw.cpp
 * Copyright 2008-2020 LibRaw LLC (info@libraw.org)
 * Created: Sat Mar  8, 2008
 *
 * LibRaw simple C++ API:  emulates call to "dcraw  [-D]  [-T] [-v] [-e] [-4]"

LibRaw is free software; you can redistribute it and/or modify
it under the terms of the one of two licenses as you choose:

1. GNU LESSER GENERAL PUBLIC LICENSE version 2.1
   (See file LICENSE.LGPL provided in LibRaw distribution archive for details).

2. COMMON DEVELOPMENT AND DISTRIBUTION LICENSE (CDDL) Version 1.0
   (See file LICENSE.CDDL provided in LibRaw distribution archive for details).


 */
#include <stdio.h>
#include <string.h>
#include <math.h>

#include "libraw/libraw.h"

#ifndef LIBRAW_WIN32_CALLS
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#endif

#ifdef LIBRAW_WIN32_CALLS
#define snprintf _snprintf
#endif

int my_progress_callback(void *unused_data, enum LibRaw_progress state,
                         int iter, int expected)
{
  if (iter == 0)
    printf("CB: state=%x, expected %d iterations\n", state, expected);
  return 0;
}

char *customCameras[] = {
    (char *)"43704960,4080,5356, 0, 0, 0, 0,0,148,0,0, Dalsa, FTF4052C Full,0",
    (char *)"42837504,4008,5344, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF4052C 3:4",
    (char *)"32128128,4008,4008, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF4052C 1:1",
    (char *)"24096096,4008,3006, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF4052C 4:3",
    (char *)"18068064,4008,2254, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF4052C 16:9",
    (char *)"67686894,5049,6703, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF5066C Full",
    (char *)"66573312,4992,6668, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF5066C 3:4",
    (char *)"49840128,4992,4992, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF5066C 1:1",
    (char *)"37400064,4992,3746, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF5066C 4:3",
    (char *)"28035072,4992,2808, 0, 0, 0, 0,0,148,0,0,Dalsa, FTF5066C 16:9",
    NULL};

int main(int ac, char *av[])
{
  int i, ret, verbose = 0, output_thumbs = 0;

  // don't use fixed size buffers in real apps!
  char outfn[1024], thumbfn[1024];

  LibRaw* RawProcessor = new LibRaw;
  RawProcessor->imgdata.params.custom_camera_strings = customCameras;
  if (ac < 2)
  {
    printf("simple_dcraw - LibRaw %s sample. Emulates dcraw [-D] [-T] [-v] "
           "[-e] [-E]\n"
           " %d cameras supported\n"
           "Usage: %s [-D] [-T] [-v] [-e] raw-files....\n"
           "\t-4 - 16-bit mode\n"
           "\t-L - list supported cameras and exit\n"
           "\t-v - verbose output\n"
           "\t-T - output TIFF files instead of .pgm/ppm\n"
           "\t-e - extract thumbnails (same as dcraw -e in separate run)\n",
           LibRaw::version(), LibRaw::cameraCount(), av[0]);
    delete RawProcessor;
    return 0;
  }

  putenv((char *)"TZ=UTC"); // dcraw compatibility, affects TIFF datestamp field

#define P1 RawProcessor->imgdata.idata
#define S RawProcessor->imgdata.sizes
#define C RawProcessor->imgdata.color
#define T RawProcessor->imgdata.thumbnail
#define P2 RawProcessor->imgdata.other
#define OUT RawProcessor->imgdata.params

  for (i = 1; i < ac; i++)
  {
    if (av[i][0] == '-')
    {
      if (av[i][1] == 'T' && av[i][2] == 0)
        OUT.output_tiff = 1;
      if (av[i][1] == 'v' && av[i][2] == 0)
        verbose++;
      if (av[i][1] == 'e' && av[i][2] == 0)
        output_thumbs++;
      if (av[i][1] == '4' && av[i][2] == 0)
        OUT.output_bps = 16;
      if (av[i][1] == 'C' && av[i][2] == 0)
        RawProcessor->set_progress_handler(my_progress_callback, NULL);
      if (av[i][1] == 'L' && av[i][2] == 0)
      {
        const char **clist = LibRaw::cameraList();
        const char **cc = clist;
        while (*cc)
        {
          printf("%s\n", *cc);
          cc++;
        }
        delete RawProcessor;
        exit(0);
      }
      continue;
    }

    if (verbose)
      printf("Processing file %s\n", av[i]);

    if ((ret = RawProcessor->open_file(av[i])) != LIBRAW_SUCCESS)
    {
      fprintf(stderr, "Cannot open_file %s: %s\n", av[i], libraw_strerror(ret));
      continue; // no recycle b/c open file will recycle itself
    }

    if (!output_thumbs) // No unpack for thumb extraction
      if ((ret = RawProcessor->unpack()) != LIBRAW_SUCCESS)
      {
        fprintf(stderr, "Cannot unpack %s: %s\n", av[i], libraw_strerror(ret));
        continue;
      }

    // thumbnail unpacking and output in the middle of main
    // image processing - for test purposes!
    if (output_thumbs)
    {
      if ((ret = RawProcessor->unpack_thumb()) != LIBRAW_SUCCESS)
      {
        fprintf(stderr, "Cannot unpack_thumb %s: %s\n", av[i],
                libraw_strerror(ret));
        if (LIBRAW_FATAL_ERROR(ret))
          continue; // skip to next file
      }
      else
      {
        snprintf(thumbfn, sizeof(thumbfn), "%s.%s", av[i],
                 T.tformat == LIBRAW_THUMBNAIL_JPEG ? "thumb.jpg"
                                                    : "thumb.ppm");

        if (verbose)
          printf("Writing thumbnail file %s\n", thumbfn);
        if (LIBRAW_SUCCESS != (ret = RawProcessor->dcraw_thumb_writer(thumbfn)))
        {
          fprintf(stderr, "Cannot write %s: %s\n", thumbfn,
                  libraw_strerror(ret));
          if (LIBRAW_FATAL_ERROR(ret))
            continue;
        }
      }
      continue;
    }

    ret = RawProcessor->dcraw_process();

    if (LIBRAW_SUCCESS != ret)
    {
      fprintf(stderr, "Cannot do postpocessing on %s: %s\n", av[i],
              libraw_strerror(ret));
      if (LIBRAW_FATAL_ERROR(ret))
        continue;
    }
    snprintf(outfn, sizeof(outfn), "%s.%s", av[i],
             OUT.output_tiff ? "tiff" : (P1.colors > 1 ? "ppm" : "pgm"));

    if (verbose)
      printf("Writing file %s\n", outfn);

    if (LIBRAW_SUCCESS != (ret = RawProcessor->dcraw_ppm_tiff_writer(outfn)))
      fprintf(stderr, "Cannot write %s: %s\n", outfn, libraw_strerror(ret));

    RawProcessor->recycle(); // just for show this call
  }
  
  delete RawProcessor;
  return 0;
}

如何在ObjectiveC/C++中打开LinearDNG？

How to open LinearDNG in ObjectiveC/C++?

macos

jpeg

core-image

dng

dcraw