private void GetBackgroundColor(IWICMetadataQueryReader wicMetadataQueryReader)
{
// 如果图片里面包含了 global palette 就需要获取 palette 和背景色
var propertyVariant = new PROPVARIANT();
wicMetadataQueryReader.GetMetadataByName("/logscrdesc/GlobalColorTableFlag", ref propertyVariant);
byte backgroundIndex = 0;
var globalPalette = (propertyVariant.Type & VARTYPE.VT_BOOL) == VARTYPE.VT_BOOL &&
propertyVariant.Value.UI1 > 0;
if (globalPalette)
{
propertyVariant = new PROPVARIANT();
wicMetadataQueryReader.GetMetadataByName("/logscrdesc/BackgroundColorIndex", ref propertyVariant);
if ((propertyVariant.Type & VARTYPE.VT_UI1) == VARTYPE.VT_UI1)
{
backgroundIndex = propertyVariant.Value.UI1;
}
var wicPalette = WicImagingFactory.CreatePalette();
WicBitmapDecoder.CopyPalette(wicPalette);
}
}
/// <summary>
/// Retrieves the metadata block or item identified by a metadata query expression.
/// </summary>
/// <param name="name">The query expression to the requested metadata block or item.</param>
/// <param name="value">The metadata block or item requested or null if not found.</param>
/// <returns>True when the metadata block or item was found, otherwise false.</returns>
/// <remarks>
/// GetMetadataByName uses metadata query expressions to access embedded metadata. For more information on the metadata query language, see the Metadata Query Language Overview.
/// <br/>
/// If multiple blocks or items exist that are expressed by the same query expression, the first metadata block or item found will be returned.
/// </remarks>
public static bool TryGetMetadataByName(this IWICMetadataQueryReader metadataQueryReader, string name, out object?value)
{
if (metadataQueryReader is null)
{
throw new NullReferenceException();
}
if (name is null)
{
throw new ArgumentNullException(nameof(name));
}
var variant = new PROPVARIANT();
try
{
metadataQueryReader.GetMetadataByName(name, ref variant);
value = PropVariantHelper.Decode(variant);
return(true);
}
catch (COMException ex) when(ex.ErrorCode == WinCodecError.PROPERTY_NOT_FOUND)
{
value = null;
return(false);
}
finally
{
PropVariantHelper.Free(variant);
}
}
public static bool TryGetMetadataByName(this IWICMetadataQueryReader meta, string name, out PropVariant val)
{
val = null;
int hr = ProxyFunctions.GetMetadataByName(meta, name, IntPtr.Zero);
if (hr >= 0)
{
val = new PropVariant();
meta.GetMetadataByName(name, val);
}
return(hr >= 0);
}
public static IEnumerable <string> GetNamesRecursive(this IWICMetadataQueryReader reader)
{
foreach (var name in reader.GetNames())
{
var val = reader.GetMetadataByName(name);
if (val is IWICMetadataQueryReader)
{
foreach (var childName in GetNamesRecursive((IWICMetadataQueryReader)val))
{
yield return(name + childName);
}
}
else
{
yield return(name);
}
}
}
public static bool TryGetMetadataByName <T>(this IWICMetadataQueryReader metadataQueryReader, string name, out T value)
{
var variant = new PROPVARIANT();
try
{
metadataQueryReader.GetMetadataByName(name, ref variant);
return(TryDecode(ref variant, out value));
}
catch (COMException ex) when(ex.ErrorCode == HResult.WINCODEC_ERR_PROPERTYNOTFOUND)
{
value = default(T);
return(false);
}
finally
{
Dispose(ref variant);
}
}
public static bool TryGetMetadataProperty <T>(this IWICMetadataQueryReader queryReader, string propertyPath, out T value)
{
if (queryReader == null)
{
throw new ArgumentNullException("queryReader");
}
value = default(T);
PROPVARIANT propvariant = default(PROPVARIANT);
int metadataByName = queryReader.GetMetadataByName(propertyPath, out propvariant);
if (-2003292352 != metadataByName)
{
GraphicsInteropNativeMethods.CheckNativeResult(metadataByName);
value = (T)((object)propvariant.Value);
propvariant.Dispose();
return(true);
}
propvariant.Dispose();
return(false);
}
/// <summary>
/// Retrieves the metadata block or item identified by a metadata query expression.
/// </summary>
/// <param name="name">The query expression to the requested metadata block or item.</param>
/// <returns>The metadata block or item requested.</returns>
/// <exception cref="COMException">Thrown when the metadata block or item was not found (HRESULT 0x88982F40).</exception>
/// <remarks>
/// GetMetadataByName uses metadata query expressions to access embedded metadata. For more information on the metadata query language, see the Metadata Query Language Overview.
/// <br/>
/// If multiple blocks or items exist that are expressed by the same query expression, the first metadata block or item found will be returned.
/// </remarks>
public static object GetMetadataByName(this IWICMetadataQueryReader metadataQueryReader, string name)
{
if (metadataQueryReader is null)
{
throw new NullReferenceException();
}
if (name is null)
{
throw new ArgumentNullException(nameof(name));
}
var variant = new PROPVARIANT();
try
{
metadataQueryReader.GetMetadataByName(name, ref variant);
return(PropVariantHelper.Decode(variant));
}
finally
{
PropVariantHelper.Free(variant);
}
}