public static StreamInfo RetrievePreview(ResourceBE attachment, uint height, uint width, RatioType ratio, SizeType size, FormatType format, out string filename)
{
if (!AttachmentBL.Instance.IsAllowedForImageMagickPreview(attachment))
{
throw new AttachmentPreviewFailedWithMimeTypeNotImplementedException(attachment.MimeType);
}
if (format != FormatType.UNDEFINED && size != SizeType.UNDEFINED && size != SizeType.ORIGINAL && size != SizeType.CUSTOM)
{
throw new AttachmentPreviewFormatConversionWithSizeNotImplementedException();
}
// check that attachment has a width and height defined
AttachmentBL.Instance.IdentifyUnknownImages(new ResourceBE[] { attachment });
#region check validity of size, width, and height parameters
// NOTE (steveb): following table describes the possible state-transitions; note that the resulting graph must acyclic to avoid infinite loops.
// BESTFIT
// -> THUMB
// -> WEBVIEW
// -> ORIGINAL
// UNDEFINED
// -> CUSTOM
// -> ORIGINAL
// THUMB
// -> ORIGINAL
// WEBVIEW
// -> ORIGINAL
// CUSTOM
// -> ORIGINAL
// ORIGINAL
again:
switch (size)
{
case SizeType.BESTFIT:
if (width == 0 && height == 0)
{
// no dimensions specified, use original
size = SizeType.ORIGINAL;
goto again;
}
if (width <= DekiContext.Current.Instance.ImageThumbPixels && height <= DekiContext.Current.Instance.ImageThumbPixels)
{
// thumbnail is big enough
size = SizeType.THUMB;
goto again;
}
else if (width <= DekiContext.Current.Instance.ImageWebviewPixels && height <= DekiContext.Current.Instance.ImageWebviewPixels)
{
// webview is big enough
size = SizeType.WEBVIEW;
goto again;
}
else
{
// use original
size = SizeType.ORIGINAL;
goto again;
}
case SizeType.CUSTOM:
if (height == 0 && width == 0)
{
// no dimensions specified, use original
size = SizeType.ORIGINAL;
goto again;
}
if ((attachment.MetaXml.ImageWidth <= width && attachment.MetaXml.ImageHeight <= height) && (attachment.MetaXml.ImageWidth >= 0 && attachment.MetaXml.ImageHeight >= 0))
{
// requested dimensions are larger than original, use original (we don't scale up!)
size = SizeType.ORIGINAL;
goto again;
}
break;
case SizeType.ORIGINAL:
width = 0;
height = 0;
break;
case SizeType.UNDEFINED:
if (height != 0 || width != 0)
{
size = SizeType.CUSTOM;
goto again;
}
else
{
size = SizeType.ORIGINAL;
goto again;
}
case SizeType.THUMB:
width = DekiContext.Current.Instance.ImageThumbPixels;
height = DekiContext.Current.Instance.ImageThumbPixels;
if ((attachment.MetaXml.ImageWidth <= width && attachment.MetaXml.ImageHeight <= height) && (attachment.MetaXml.ImageWidth >= 0 && attachment.MetaXml.ImageHeight >= 0))
{
size = SizeType.ORIGINAL;
goto again;
}
break;
case SizeType.WEBVIEW:
width = DekiContext.Current.Instance.ImageWebviewPixels;
height = DekiContext.Current.Instance.ImageWebviewPixels;
if ((attachment.MetaXml.ImageWidth <= width && attachment.MetaXml.ImageHeight <= height) && (attachment.MetaXml.ImageWidth >= 0 && attachment.MetaXml.ImageHeight >= 0))
{
size = SizeType.ORIGINAL;
goto again;
}
break;
}
#endregion
// Asking to convert to the same format as original
if (format != FormatType.UNDEFINED && format == ResolvePreviewFormat(attachment.MimeType))
{
format = FormatType.UNDEFINED;
}
//Determine if the result is capable of being cached
bool cachable = (
format == FormatType.UNDEFINED && //No format conversion
ratio != RatioType.VARIABLE && //must be a fixed aspect ratio or not provided
(size == SizeType.THUMB || size == SizeType.WEBVIEW) //must be one of the known cached thumb sizes.
);
// load image
StreamInfo result = null;
try {
if (size == SizeType.ORIGINAL && format == FormatType.UNDEFINED)
{
result = DekiContext.Current.Instance.Storage.GetFile(attachment, SizeType.ORIGINAL, false);
}
else
{
bool cached = false;
//The type of image is based on uploaded file's mimetype
if (format == FormatType.UNDEFINED)
{
format = ResolvePreviewFormat(attachment.MimeType);
}
// check if image can be taken from the cache
if (cachable)
{
result = GetCachedThumb(attachment, size);
cached = (result != null);
}
// load image if we haven't yet
if (result == null)
{
result = DekiContext.Current.Instance.Storage.GetFile(attachment, SizeType.ORIGINAL, false);
if (result != null)
{
result = BuildThumb(attachment, result, format, ratio, width, height);
}
}
// store result if possible and needed
if (cachable && !cached && (result != null))
{
SaveCachedThumb(attachment, size, result);
result = GetCachedThumb(attachment, size);
}
}
if (result == null)
{
ThrowOnBadPreviewImage();
}
// full filename for response content-disposition header
switch (size)
{
case SizeType.CUSTOM:
filename = string.Format("{0}_({1}x{2}){3}", attachment.Name, width == 0 ? "" : width.ToString(), height == 0 ? "" : height.ToString(), attachment.FilenameExtension == string.Empty ? string.Empty : "." + attachment.FilenameExtension);
break;
case SizeType.ORIGINAL:
filename = attachment.Name;
break;
case SizeType.BESTFIT:
case SizeType.THUMB:
case SizeType.UNDEFINED:
case SizeType.WEBVIEW:
default:
filename = string.Format("{0}_({1}){2}", attachment.Name, size.ToString().ToLowerInvariant(), attachment.FilenameExtension == string.Empty ? string.Empty : "." + attachment.FilenameExtension);
break;
}
if (format != FormatType.UNDEFINED)
{
filename = Path.ChangeExtension(filename, format.ToString().ToLowerInvariant());
}
return(result);
} catch {
if (result != null)
{
result.Close();
}
throw;
}
}
