read_region()

std::vector< Kakshya::DataVariant > MayaFlux::IO::ImageReader::read_region ( const FileRegion &  region )

overridevirtual

Read a specific region of data.

Parameters

region

Region descriptor.

Returns

DataVariant vector containing the requested data.

Implements MayaFlux::IO::FileReader.

Definition at line 347 of file ImageReader.cpp.

{
    if (!m_is_open || !m_image_data) {
        m_last_error = "No image open";
        return {};
    }
 
    if (region.start_coordinates.size() < 2 || region.end_coordinates.size() < 2) {
        m_last_error = "Invalid region coordinates for image";
        return {};
    }
 
    auto x_start = static_cast<uint32_t>(region.start_coordinates[0]);
    auto y_start = static_cast<uint32_t>(region.start_coordinates[1]);
    auto x_end = static_cast<uint32_t>(region.end_coordinates[0]);
    auto y_end = static_cast<uint32_t>(region.end_coordinates[1]);
 
    if (x_end > m_image_data->width || y_end > m_image_data->height) {
        m_last_error = "Region out of bounds";
        return {};
    }
 
    uint32_t region_width = x_end - x_start;
    uint32_t region_height = y_end - y_start;
 
    const size_t bytes_per_pixel = m_image_data->byte_size() / m_image_data->element_count() * m_image_data->channels;
    const size_t bytes_per_elem = m_image_data->byte_size() / m_image_data->element_count();
    const size_t pixel_stride_bytes = bytes_per_elem * m_image_data->channels;
 
    std::vector<uint8_t> region_data(
        static_cast<size_t>(region_width) * region_height * pixel_stride_bytes);
 
    const auto* src = static_cast<const uint8_t*>(m_image_data->data());
 
    for (uint32_t y = 0; y < region_height; ++y) {
        size_t src_offset = (static_cast<size_t>((y_start + y) * m_image_data->width + x_start)) * pixel_stride_bytes;
        size_t dst_offset = static_cast<size_t>(y * region_width) * pixel_stride_bytes;
        size_t row_size = static_cast<size_t>(region_width) * pixel_stride_bytes;
        std::memcpy(
            region_data.data() + dst_offset,
            src + src_offset,
            row_size);
    }
 
    return { region_data };
}

References MayaFlux::IO::FileRegion::end_coordinates, m_image_data, m_is_open, m_last_error, and MayaFlux::IO::FileRegion::start_coordinates.