Image.h

// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2023 www.open3d.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------

#pragma once

#include <Eigen/Core>
#include <memory>
#include <vector>

#include "open3d/geometry/Geometry2D.h"
#include "open3d/utility/Logging.h"

namespace open3d {

namespace camera {
class PinholeCameraIntrinsic;
}

namespace geometry {

class Image;

/// Typedef and functions for ImagePyramid.
typedef std::vector<std::shared_ptr<Image>> ImagePyramid;

/// \class Image
///
/// \brief The Image class stores image with customizable width, height, num of
/// channels and bytes per channel.
class Image : public Geometry2D {
public:
    /// \enum ColorToIntensityConversionType
    ///
    /// \brief Specifies whether R, G, B channels have the same weight when
    /// converting to intensity. Only used for Image with 3 channels.
    ///
    /// When `Weighted` is used R, G, B channels are weighted according to the
    /// Digital ITU BT.601 standard: I = 0.299 * R + 0.587 * G + 0.114 * B.
    enum class ColorToIntensityConversionType {
        /// R, G, B channels have equal weights.
        Equal,
        /// Weighted R, G, B channels: I = 0.299 * R + 0.587 * G + 0.114 * B.
        Weighted,
    };

    /// \enum FilterType
    ///
    /// \brief Specifies the Image filter type.
    enum class FilterType {
        /// Gaussian filter of size 3 x 3.
        Gaussian3,
        /// Gaussian filter of size 5 x 5.
        Gaussian5,
        /// Gaussian filter of size 7 x 7.
        Gaussian7,
        /// Sobel filter along X-axis.
        Sobel3Dx,
        /// Sobel filter along Y-axis.
        Sobel3Dy
    };

public:
    /// \brief Default Constructor.
    Image() : Geometry2D(Geometry::GeometryType::Image) {}
    ~Image() override {}

public:
    Image &Clear() override;
    bool IsEmpty() const override;
    Eigen::Vector2d GetMinBound() const override;
    Eigen::Vector2d GetMaxBound() const override;

    /// \brief Test if coordinate `(u, v)` is located in the inner_marge of the
    /// image.
    ///
    /// \param u Coordinate along the width dimension.
    /// \param v Coordinate along the height dimension.
    /// \param inner_margin The inner margin from the image boundary.
    /// \return Returns `true` if coordinate `(u, v)` is located in the
    /// inner_marge of the image.
    bool TestImageBoundary(double u, double v, double inner_margin = 0.0) const;

public:
    /// Returns `true` if the Image has valid data.
    virtual bool HasData() const {
        return width_ > 0 && height_ > 0 &&
               data_.size() == size_t(height_ * BytesPerLine());
    }

    /// \brief Prepare Image properties and allocate Image buffer.
    Image &Prepare(int width,
                   int height,
                   int num_of_channels,
                   int bytes_per_channel) {
        width_ = width;
        height_ = height;
        num_of_channels_ = num_of_channels;
        bytes_per_channel_ = bytes_per_channel;
        AllocateDataBuffer();
        return *this;
    }

    /// \brief Returns data size per line (row, or the width) in bytes.
    int BytesPerLine() const {
        return width_ * num_of_channels_ * bytes_per_channel_;
    }

    /// Function to access the bilinear interpolated float value of a
    /// (single-channel) float image.
    /// Returns a tuple, where the first bool indicates if the u,v coordinates
    /// are within the image dimensions, and the second double value is the
    /// interpolated pixel value.
    std::pair<bool, double> FloatValueAt(double u, double v) const;

    /// Factory function to create a float image composed of multipliers that
    /// convert depth values into camera distances (ImageFactory.cpp)
    /// The multiplier function M(u,v) is defined as:
    /// M(u, v) = sqrt(1 + ((u - cx) / fx) ^ 2 + ((v - cy) / fy) ^ 2)
    /// This function is used as a convenient function for performance
    /// optimization in volumetric integration (see
    /// Core/Integration/TSDFVolume.h).
    static std::shared_ptr<Image>
    CreateDepthToCameraDistanceMultiplierFloatImage(
            const camera::PinholeCameraIntrinsic &intrinsic);

    /// Return a gray scaled float type image.
    std::shared_ptr<Image> CreateFloatImage(
            Image::ColorToIntensityConversionType type =
                    Image::ColorToIntensityConversionType::Weighted) const;

    /// Function to access the raw data of a single-channel Image.
    template <typename T>
    T *PointerAt(int u, int v) const;

    /// Function to access the raw data of a multi-channel Image.
    template <typename T>
    T *PointerAt(int u, int v, int ch) const;

    /// Reinterpret the internal data buffer. The resulting type's size must be
    /// the same as bytes_per_channel_. This is similar to PointerAt<T>(0, 0).
    template <class T>
    T *PointerAs() const {
        if (sizeof(T) != bytes_per_channel_) {
            utility::LogError("sizeof(T) != byte_per_channel_: {} != {}.",
                              sizeof(T), bytes_per_channel_);
        }
        return (T *)(data_.data());
    }

    std::shared_ptr<Image> ConvertDepthToFloatImage(
            double depth_scale = 1000.0, double depth_trunc = 3.0) const;

    std::shared_ptr<Image> Transpose() const;

    /// Function to flip image horizontally (from left to right).
    std::shared_ptr<Image> FlipHorizontal() const;
    /// Function to flip image vertically (upside down).
    std::shared_ptr<Image> FlipVertical() const;

    /// Function to filter image with pre-defined filtering type.
    std::shared_ptr<Image> Filter(Image::FilterType type) const;

    /// Function to filter image with arbitrary dx, dy separable filters.
    std::shared_ptr<Image> Filter(const std::vector<double> &dx,
                                  const std::vector<double> &dy) const;

    std::shared_ptr<Image> FilterHorizontal(
            const std::vector<double> &kernel) const;

    /// Function to 2x image downsample using simple 2x2 averaging.
    std::shared_ptr<Image> Downsample() const;

    /// Function to dilate 8bit mask map.
    std::shared_ptr<Image> Dilate(int half_kernel_size = 1) const;

    /// Function to linearly transform pixel intensities
    /// image_new = scale * image + offset.
    Image &LinearTransform(double scale = 1.0, double offset = 0.0);

    /// Function to clipping pixel intensities.
    ///
    /// \param min is lower bound.
    /// \param max is upper bound.
    Image &ClipIntensity(double min = 0.0, double max = 1.0);

    /// Function to change data types of image
    /// crafted for specific usage such as
    /// single channel float image -> 8-bit RGB or 16-bit depth image.
    template <typename T>
    std::shared_ptr<Image> CreateImageFromFloatImage() const;

    /// Function to filter image pyramid.
    static ImagePyramid FilterPyramid(const ImagePyramid &input,
                                      Image::FilterType type);

    /// Function to create image pyramid.
    ImagePyramid CreatePyramid(size_t num_of_levels,
                               bool with_gaussian_filter = true) const;

    /// Function to create a depthmap boundary mask from depth image.
    std::shared_ptr<Image> CreateDepthBoundaryMask(
            double depth_threshold_for_discontinuity_check = 0.1,
            int half_dilation_kernel_size_for_discontinuity_map = 3) const;

protected:
    void AllocateDataBuffer() {
        data_.resize(width_ * height_ * num_of_channels_ * bytes_per_channel_);
    }

public:
    /// Width of the image.
    int width_ = 0;
    /// Height of the image.
    int height_ = 0;
    /// Number of channels in the image.
    int num_of_channels_ = 0;
    /// Number of bytes per channel.
    int bytes_per_channel_ = 0;
    /// Image storage buffer.
    std::vector<uint8_t> data_;
};

}  // namespace geometry
}  // namespace open3d