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Tiny OpenEXR image library.

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tinyexr is a small, single header-only library to load and save OpenEXR (.exr) images. tinyexr is written in portable C++ (no library dependency except for STL), thus tinyexr is good to embed into your application. To use tinyexr, simply copy tinyexr.h, miniz.c and miniz.h(for zlib. You can use system-installed zlib instead of miniz, or the zlib implementation included in stb_image[_write].h. Controlled with TINYEXR_USE_MINIZ and TINYEXR_USE_STB_ZLIB compile flags) into your project.

Security

TinyEXR does not use C++ exception.

TinyEXR now does not use assert from v1.0.4(2023/06/04), except for miniz's assert. (We plan to use wuff's zlib for better security and performance)

TinyEXR is fuzz tested and currently no security issues(No seg fault for any malcious/corrupted input EXR data) as of v1.0.7.

Features

Current status of tinyexr is:

Supported platform

Requirements

Use case

New TinyEXR (v0.9.5+)

Older TinyEXR (v0.9.0)

Examples

Experimental

Usage

NOTE: API is still subject to change. See the source code for details.

Include tinyexr.h with TINYEXR_IMPLEMENTATION flag (do this only for one .cc file).

//Please include your own zlib-compatible API header before
//including `tinyexr.h` when you disable `TINYEXR_USE_MINIZ`
//#define TINYEXR_USE_MINIZ 0
//#include "zlib.h"
//Or, if your project uses `stb_image[_write].h`, use their
//zlib implementation:
//#define TINYEXR_USE_STB_ZLIB 1
#define TINYEXR_IMPLEMENTATION
#include "tinyexr.h"

Compile flags

Quickly reading RGB(A) EXR file.

  const char* input = "asakusa.exr";
  float* out; // width * height * RGBA
  int width;
  int height;
  const char* err = NULL; // or nullptr in C++11

  int ret = LoadEXR(&out, &width, &height, input, &err);

  if (ret != TINYEXR_SUCCESS) {
    if (err) {
       fprintf(stderr, "ERR : %s\n", err);
       FreeEXRErrorMessage(err); // release memory of error message.
    }
  } else {
    ...
    free(out); // release memory of image data
  }

Reading layered RGB(A) EXR file.

If you want to read EXR image with layer info (channel has a name with delimiter .), please use LoadEXRWithLayer API.

You need to know layer name in advance (e.g. through EXRLayers API).

  const char* input = ...;
  const char* layer_name = "diffuse"; // or use EXRLayers to get list of layer names in .exr
  float* out; // width * height * RGBA
  int width;
  int height;
  const char* err = NULL; // or nullptr in C++11

  // will read `diffuse.R`, `diffuse.G`, `diffuse.B`, (`diffuse.A`) channels
  int ret = LoadEXRWithLayer(&out, &width, &height, input, layer_name, &err);

  if (ret != TINYEXR_SUCCESS) {
    if (err) {
       fprintf(stderr, "ERR : %s\n", err);
       FreeEXRErrorMessage(err); // release memory of error message.
    }
  } else {
    ...
    free(out); // release memory of image data
  }

Loading Singlepart EXR from a file.

Scanline and tiled format are supported.

  // 1. Read EXR version.
  EXRVersion exr_version;

  int ret = ParseEXRVersionFromFile(&exr_version, argv[1]);
  if (ret != 0) {
    fprintf(stderr, "Invalid EXR file: %s\n", argv[1]);
    return -1;
  }

  if (exr_version.multipart) {
    // must be multipart flag is false.
    return -1;
  }

  // 2. Read EXR header
  EXRHeader exr_header;
  InitEXRHeader(&exr_header);

  const char* err = NULL; // or `nullptr` in C++11 or later.
  ret = ParseEXRHeaderFromFile(&exr_header, &exr_version, argv[1], &err);
  if (ret != 0) {
    fprintf(stderr, "Parse EXR err: %s\n", err);
    FreeEXRErrorMessage(err); // free's buffer for an error message
    return ret;
  }

  // // Read HALF channel as FLOAT.
  // for (int i = 0; i < exr_header.num_channels; i++) {
  //   if (exr_header.pixel_types[i] == TINYEXR_PIXELTYPE_HALF) {
  //     exr_header.requested_pixel_types[i] = TINYEXR_PIXELTYPE_FLOAT;
  //   }
  // }

  EXRImage exr_image;
  InitEXRImage(&exr_image);

  ret = LoadEXRImageFromFile(&exr_image, &exr_header, argv[1], &err);
  if (ret != 0) {
    fprintf(stderr, "Load EXR err: %s\n", err);
    FreeEXRHeader(&exr_header);
    FreeEXRErrorMessage(err); // free's buffer for an error message
    return ret;
  }

  // 3. Access image data
  // `exr_image.images` will be filled when EXR is scanline format.
  // `exr_image.tiled` will be filled when EXR is tiled format.

  // 4. Free image data
  FreeEXRImage(&exr_image);
  FreeEXRHeader(&exr_header);

Loading Multipart EXR from a file.

Scanline and tiled format are supported.

  // 1. Read EXR version.
  EXRVersion exr_version;

  int ret = ParseEXRVersionFromFile(&exr_version, argv[1]);
  if (ret != 0) {
    fprintf(stderr, "Invalid EXR file: %s\n", argv[1]);
    return -1;
  }

  if (!exr_version.multipart) {
    // must be multipart flag is true.
    return -1;
  }

  // 2. Read EXR headers in the EXR.
  EXRHeader **exr_headers; // list of EXRHeader pointers.
  int num_exr_headers;
  const char *err = NULL; // or nullptr in C++11 or later

  // Memory for EXRHeader is allocated inside of ParseEXRMultipartHeaderFromFile,
  ret = ParseEXRMultipartHeaderFromFile(&exr_headers, &num_exr_headers, &exr_version, argv[1], &err);
  if (ret != 0) {
    fprintf(stderr, "Parse EXR err: %s\n", err);
    FreeEXRErrorMessage(err); // free's buffer for an error message
    return ret;
  }

  printf("num parts = %d\n", num_exr_headers);


  // 3. Load images.

  // Prepare array of EXRImage.
  std::vector<EXRImage> images(num_exr_headers);
  for (int i =0; i < num_exr_headers; i++) {
    InitEXRImage(&images[i]);
  }

  ret = LoadEXRMultipartImageFromFile(&images.at(0), const_cast<const EXRHeader**>(exr_headers), num_exr_headers, argv[1], &err);
  if (ret != 0) {
    fprintf(stderr, "Parse EXR err: %s\n", err);
    FreeEXRErrorMessage(err); // free's buffer for an error message
    return ret;
  }

  printf("Loaded %d part images\n", num_exr_headers);

  // 4. Access image data
  // `exr_image.images` will be filled when EXR is scanline format.
  // `exr_image.tiled` will be filled when EXR is tiled format.

  // 5. Free images
  for (int i =0; i < num_exr_headers; i++) {
    FreeEXRImage(&images.at(i));
  }

  // 6. Free headers.
  for (int i =0; i < num_exr_headers; i++) {
    FreeEXRHeader(exr_headers[i]);
    free(exr_headers[i]);
  }
  free(exr_headers);

Saving Scanline EXR file.

  // See `examples/rgbe2exr/` for more details.
  bool SaveEXR(const float* rgb, int width, int height, const char* outfilename) {

    EXRHeader header;
    InitEXRHeader(&header);

    EXRImage image;
    InitEXRImage(&image);

    image.num_channels = 3;

    std::vector<float> images[3];
    images[0].resize(width * height);
    images[1].resize(width * height);
    images[2].resize(width * height);

    // Split RGBRGBRGB... into R, G and B layer
    for (int i = 0; i < width * height; i++) {
      images[0][i] = rgb[3*i+0];
      images[1][i] = rgb[3*i+1];
      images[2][i] = rgb[3*i+2];
    }

    float* image_ptr[3];
    image_ptr[0] = &(images[2].at(0)); // B
    image_ptr[1] = &(images[1].at(0)); // G
    image_ptr[2] = &(images[0].at(0)); // R

    image.images = (unsigned char**)image_ptr;
    image.width = width;
    image.height = height;

    header.num_channels = 3;
    header.channels = (EXRChannelInfo *)malloc(sizeof(EXRChannelInfo) * header.num_channels);
    // Must be (A)BGR order, since most of EXR viewers expect this channel order.
    strncpy(header.channels[0].name, "B", 255); header.channels[0].name[strlen("B")] = '\0';
    strncpy(header.channels[1].name, "G", 255); header.channels[1].name[strlen("G")] = '\0';
    strncpy(header.channels[2].name, "R", 255); header.channels[2].name[strlen("R")] = '\0';

    header.pixel_types = (int *)malloc(sizeof(int) * header.num_channels);
    header.requested_pixel_types = (int *)malloc(sizeof(int) * header.num_channels);
    for (int i = 0; i < header.num_channels; i++) {
      header.pixel_types[i] = TINYEXR_PIXELTYPE_FLOAT; // pixel type of input image
      header.requested_pixel_types[i] = TINYEXR_PIXELTYPE_HALF; // pixel type of output image to be stored in .EXR
    }

    const char* err = NULL; // or nullptr in C++11 or later.
    int ret = SaveEXRImageToFile(&image, &header, outfilename, &err);
    if (ret != TINYEXR_SUCCESS) {
      fprintf(stderr, "Save EXR err: %s\n", err);
      FreeEXRErrorMessage(err); // free's buffer for an error message
      return ret;
    }
    printf("Saved exr file. [ %s ] \n", outfilename);

    free(rgb);

    free(header.channels);
    free(header.pixel_types);
    free(header.requested_pixel_types);

  }

Reading deep image EXR file. See example/deepview for actual usage.

  const char* input = "deepimage.exr";
  const char* err = NULL; // or nullptr
  DeepImage deepImage;

  int ret = LoadDeepEXR(&deepImage, input, &err);

  // access to each sample in the deep pixel.
  for (int y = 0; y < deepImage.height; y++) {
    int sampleNum = deepImage.offset_table[y][deepImage.width-1];
    for (int x = 0; x < deepImage.width-1; x++) {
      int s_start = deepImage.offset_table[y][x];
      int s_end   = deepImage.offset_table[y][x+1];
      if (s_start >= sampleNum) {
        continue;
      }
      s_end = (s_end < sampleNum) ? s_end : sampleNum;
      for (int s = s_start; s < s_end; s++) {
        float val = deepImage.image[depthChan][y][s];
        ...
      }
    }
  }

deepview

examples/deepview is simple deep image viewer in OpenGL.

DeepViewExample

TinyEXR extension

ZFP

NOTE

TinyEXR adds ZFP compression as an experimemtal support (Linux and MacOSX only).

ZFP only supports FLOAT format pixel, and its image width and height must be the multiple of 4, since ZFP compresses pixels with 4x4 pixel block.

Setup

Checkout zfp repo as an submodule.

$ git submodule update --init

Build

Then build ZFP

$ cd deps/ZFP
$ mkdir -p lib   # Create `lib` directory if not exist
$ make

Set 1 to TINYEXT_USE_ZFP define in tinyexr.h

Build your app with linking deps/ZFP/lib/libzfp.a

ZFP attribute

For ZFP EXR image, the following attribute must exist in its EXR image.

And the one of following attributes must exist in EXR, depending on the zfpCompressionType value.

Note on ZFP compression.

At least ZFP code itself works well on big endian machine.

Unit tests

See test/unit directory.

TODO

Contribution is welcome!

Python bindings

pytinyexr is available: https://pypi.org/project/pytinyexr/ (loading only as of 0.9.1)

Similar or related projects

License

3-clause BSD

tinyexr uses miniz, which is developed by Rich Geldreich richgel99@gmail.com, and licensed under public domain.

tinyexr tools uses stb, which is licensed under public domain: https://github.com/nothings/stb tinyexr uses some code from OpenEXR, which is licensed under 3-clause BSD license. tinyexr uses nanozlib and wuffs, whose are licensed unnder Apache 2.0 license.

Author(s)

Syoyo Fujita (syoyo@lighttransport.com)

Contributor(s)