/// <summary>
/// This function allocates and initializes an incremental-decoder object, which
/// will output the RGB/A samples specified by '<paramref name="colorspace"/>' into a preallocated
/// buffer '<paramref name="output_buffer"/>'. The size of this buffer is at least
/// '<paramref name="output_buffer_size"/>' and the stride (distance in bytes between two scanlines)
/// is specified by '<paramref name="output_stride"/>'
/// </summary>
/// <remarks>
/// Additionally, <paramref name="output_buffer"/> can be passed NULL in which case the output
/// buffer will be allocated automatically when the decoding starts. The
/// '<paramref name="colorspace"/>' is taken into account for allocating this buffer. All other
/// parameters are ignored.
/// </remarks>
/// <exception cref="InvalidProgramException">Unknown error occured.</exception>
/// <exception cref="NotSupportedException"><paramref name="colorspace"/> is not RGB(A) colorspace</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="colorspace"/> is not a valid value</exception>
/// <returns><see cref="WebpImageDecoder"/></returns>
public static WebpImageDecoder CreateDecoderForRGBX(ILibwebp library, Colorspace colorspace, IntPtr output_buffer, UIntPtr output_buffer_size, int output_stride)
{
WebpImageDecoder result;
if (colorspace >= Colorspace.MODE_LAST)
{
throw new ArgumentOutOfRangeException(nameof(colorspace));
}
if (colorspace == Colorspace.MODE_YUVA || colorspace == Colorspace.MODE_YUV)
{
throw new NotSupportedException();
}
else
{
var ptr = library.WebPINewRGB(colorspace, output_buffer, output_buffer_size, output_stride);
if (ptr == IntPtr.Zero)
{
throw new Exception();
}
else
{
result = new WebpImageDecoder(library, false);
result.decoder = ptr;
}
}
if (result == null)
{
throw new InvalidProgramException();
}
return(result);
}
/// <summary>Decrease the reference count toward the loaded native library.</summary>
/// <remarks>
/// When reference count reaches 0, the native library will be unloaded.
/// Calling this method does not guarantee the native library to be unloaded immediately.
/// This method will not dispose any objects (Eg: <seealso cref="WebpImageDecoder"/>) created from this <see cref="WebpFactory"/> instance, either.
/// </remarks>
public void Dispose()
{
if (this.disposed)
{
return;
}
this.disposed = true;
Libwebp.Deinit(this.library);
this.library = null;
}
/// <summary>
/// Initialize a new instance of <see cref="WebpFactory"/> from loaded native library.
/// </summary>
/// <param name="library">The native library.</param>
/// <exception cref="ArgumentException">Throws when the given native library is not from <seealso cref="Libwebp.Init(string)"/>.</exception>
public WebpFactory(ILibwebp library)
{
this.disposed = false;
if (library is Libwebp lib)
{
lib.IncreaseReferenceCount();
this.library = library;
}
else
{
throw new ArgumentException(nameof(library));
}
}
/// <summary>
/// Initialize a new instance of <see cref="WebpFactory"/>.
/// </summary>
/// <param name="libraryPath">The path to the native library.</param>
public WebpFactory(string libraryPath)
{
this.disposed = false;
this.library = Libwebp.Init(libraryPath);
}
private WebpImageDecoder(ILibwebp library, in bool dummy)
/// <summary>
/// This function allocates and initializes an incremental-decoder object, which
/// will output the RGB/A samples specified by '<paramref name="colorspace"/>' into a preallocated internal buffer.
/// </summary>
/// <remarks>
/// Equivalent to <seealso cref="CreateDecoderForRGBX(ILibwebp, Colorspace, IntPtr, UIntPtr, int)"/>, with 'output_buffer' is NULL.
/// Use <seealso cref="GetDecodedImage(ref int, out int, out int, out int, out IntPtr)"/> or <seealso cref="GetDecodedImage(ref int, out int, out int, out int, out ReadOnlySpan{byte})"/>
/// to obtain the decoded data.
/// </remarks>
/// <exception cref="InvalidProgramException">Unknown error occured.</exception>
/// <exception cref="NotSupportedException"><paramref name="colorspace"/> is not RGB(A) colorspace</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="colorspace"/> is not a valid value</exception>
/// <returns><see cref="WebpImageDecoder"/></returns>
public static WebpImageDecoder CreateDecoderForRGBX(ILibwebp library, Colorspace colorspace)
=> CreateDecoderForRGBX(library, colorspace, IntPtr.Zero, UIntPtr.Zero, 0);
