Magnum::Trade::StbImageConverter class

#include <MagnumPlugins/StbImageConverter/StbImageConverter.h>

Usage

This plugin depends on the Trade library and is built if MAGNUM_WITH_STBIMAGECONVERTER is enabled when building Magnum Plugins. To use as a dynamic plugin, load one of the "StbBmpImageConverter", "StbHdrImageConverter", "StbPngImageConverter", "StbTgaImageConverter" plugins via Corrade::PluginManager::Manager. If you would load the plugin as just "StbImageConverter", it won't be able to guess the desired output format.

Additionally, if you're using Magnum as a CMake subproject, bundle the magnum-plugins repository and do the following:

set(MAGNUM_WITH_STBIMAGECONVERTER ON CACHE BOOL "" FORCE)
add_subdirectory(magnum-plugins EXCLUDE_FROM_ALL)

# So the dynamically loaded plugin gets built implicitly
add_dependencies(your-app MagnumPlugins::StbImageConverter)

To use as a static plugin or as a dependency of another plugin with CMake, put FindMagnumPlugins.cmake into your modules/ directory, request the StbImageConverter component of the MagnumPlugins package and link to the MagnumPlugins::StbImageConverter target:

find_package(MagnumPlugins REQUIRED StbImageConverter)

# ...
target_link_libraries(your-app PRIVATE MagnumPlugins::StbImageConverter)

See Downloading and building plugins, Plugin usage with CMake, Loading and using plugins and File format support for more information.

Behavior and limitations

Supports the following input and output format combinations:

• Windows Bitmap (*.bmp) if the plugin was loaded as StbBmpImageConverter / BmpImageConverter, if convertToFile() was called with the corresponding extension or if Format::Bmp was passed to the constructor. Accepts PixelFormat::R8Unorm, PixelFormat::RG8Unorm, PixelFormat::RGB8Unorm and PixelFormat::RGBA8Unorm. Single- and two-channel inputs are converted to three-channel with the the first channel repeated three times (and second ignored), four-channel input loses alpha.
• Radiance HDR (*.hdr) if the plugin was loaded as StbHdrImageConverter / HdrImageConverter, if convertToFile() was called with the corresponding extension or if Format::Hdr was passed to the constructor. Accepts PixelFormat::R32F, PixelFormat::RG32F, PixelFormat::RGB32F or PixelFormat::RGBA32F. R and RG inputs are converted to three-channel RRR with G ignored, four-channel input loses alpha.
• JPEG (*.jpg, *.jpe, *.jpeg) if the plugin was loaded as StbJpegImageConverter / JpegImageConverter, if convertToFile() was called with one of the corresponding extensions or if Format::Jpeg was passed to the constructor. Accepts PixelFormat::R8Unorm, PixelFormat::RG8Unorm, PixelFormat::RGB8Unorm and PixelFormat::RGBA8Unorm. Single- and two-channel inputs are converted to three-channel with the first channel repeated three times (and second ignored), four-channel input loses alpha.
• Portable Network Graphics (*.png) if the plugin was loaded as StbPngImageConverter / PngImageConverter, if convertToFile() was called with the corresponding extension or if Format::Png was passed to the constructor. Accepts PixelFormat::R8Unorm, PixelFormat::RG8Unorm, PixelFormat::RGB8Unorm and PixelFormat::RGBA8Unorm, output has the same amount of channels as input.
• Truevision TGA (*.tga, *.vda, *.icb, *.vst) if the plugin was loaded as StbTgaImageConverter / TgaImageConverter, if convertToFile() was called with one of the corresponding extensions or if Format::Tga was passed to the constructor. Accepts PixelFormat::R8Unorm, PixelFormat::RG8Unorm, PixelFormat::RGB8Unorm and PixelFormat::RGBA8Unorm, output has the same amount of channels as input.

While the plugin provides generic aliases such as PngImageConverter, it may generate slightly larger files and the performance might be worse than when using plugins dedicated for given format such as PngImageConverter.

If the conversion results in lost channels (such as saving RGBA to a JPEG, losing the alpha in process), a warning is printed to the output.

None of the formats supported by this plugin have any way to distinguish between 2D and 1D array images. If an image has ImageFlag2D::Array set, a warning is printed and the file is saved as a regular 2D image.

Depending on the alias under which the plugin was loaded or the Format passed to constructor, extension() is one of "bmp", "hdr", "jpg", "png" or "tga", picking always the most common for each format; the mimeType() is one of "image/bmp", "image/vnd.radiance", "image/jpeg", "image/png" or "image/x-tga". Returned values are consistent with what JpegImageConverter, PngImageConverter and TgaImageConverter use, see their documentation for more information. If the plugin is loaded as StbImageConverter or no format is passed to the constructor, both extension() and mimeType() return an empty string. The returned values are also independent of what file extension is used in a call to convertToFile().

The plugin recognizes ImageConverterFlag::Quiet, which will cause all conversion warnings to be suppressed.

Plugin-specific configuration

For some formats, it's possible to tune various output options through configuration(). See below for all options and their default values:

[configuration]

# Compression quality for JPEG output (0 - 1, 1 is the best). Corresponds to
# the same option in JpegImageConverter.
jpegQuality=0.8

See Editing plugin-specific configuration for more information and an example showing how to edit the configuration values.

Base classes

class AbstractImageConverter

Base for image converter plugins.

Public types

enum class Format: Int { Bmp = 1, Jpeg, Hdr, Png, Tga }

Output file format.

Constructors, destructors, conversion operators

StbImageConverter(Format format) explicit

Default constructor.

StbImageConverter(PluginManager::AbstractManager& manager, const Containers::StringView& plugin) explicit

Plugin manager constructor.

Enum documentation

Function documentation