@@ -10,6 +10,13 @@ namespace CodeCave.Revit.Toolkit.Thumbnails
1010 /// </summary>
1111 public class DwgThumbnailExtractor : ThumbnailExtractor
1212 {
13+ private static readonly Color ColorBlack = Color . Black ;
14+
15+ private static readonly Color ColorWhite = Color . White ;
16+
17+ private bool RetainBackgroudColor { get ; set ; } = true ;
18+
19+ /// <inheritdoc/>
1320 public override byte [ ] ExtractThumbnailBytes ( Stream stream )
1421 {
1522 using var binaryReader = new BinaryReader ( stream ) ;
@@ -24,51 +31,102 @@ public override byte[] ExtractThumbnailBytes(Stream stream)
2431
2532 for ( short i = 1 ; i <= byteCount ; i ++ )
2633 {
27- var imageCode = binaryReader . ReadByte ( ) ;
28- var imageHeaderStart = binaryReader . ReadInt32 ( ) ;
29- var imageHeaderSize = binaryReader . ReadInt32 ( ) ;
34+ var thumbInfo = new ThumbnailInfo
35+ {
36+ Type = binaryReader . ReadByte ( ) ,
37+ Start = binaryReader . ReadInt32 ( ) ,
38+ Length = binaryReader . ReadInt32 ( ) ,
39+ } ;
3040
3141#pragma warning disable CC0120 // default just skips to the next byte
32- switch ( imageCode )
42+ switch ( thumbInfo . Type )
3343 {
3444 // PNG thumbnail - ACAD 2013 and later
35- case ThumbnailImageCodes . PNG :
45+ case ThumbnailInfo . PngType :
3646 var ms2013 = new MemoryStream ( ) ;
37- stream . Seek ( imageHeaderStart , SeekOrigin . Begin ) ;
38- stream . CopyTo ( ms2013 , imageHeaderSize ) ;
47+ stream . Seek ( thumbInfo . Start , SeekOrigin . Begin ) ;
48+ stream . CopyTo ( ms2013 , thumbInfo . Length ) ;
3949 var byte2013 = ms2013 . ToArray ( ) ;
4050
4151 return byte2013 ;
4252
4353 // BMP Preview (2010 file format and lower)
44- case ThumbnailImageCodes . BMP :
45- binaryReader . ReadBytes ( 0xe ) ;
46- var biBitCount = binaryReader . ReadUInt16 ( ) ;
47- binaryReader . ReadBytes ( 4 ) ;
48- var biSizeImage = binaryReader . ReadUInt32 ( ) ;
49-
50- stream . Seek ( imageHeaderStart , SeekOrigin . Begin ) ;
51- var bitmapBuffer = binaryReader . ReadBytes ( imageHeaderSize ) ;
52- var bitCountRaw = ( biBitCount < 9 ) ? 4 * Math . Pow ( 2 , biBitCount ) : 0 ;
53- var bitCount = Math . Truncate ( bitCountRaw ) ;
54- var colorTableSize = Convert . ToUInt32 ( bitCount ) ;
55- using ( var ms = new MemoryStream ( ) )
54+ case ThumbnailInfo . BmpType :
55+
56+ for ( var intCnt = 0 ; intCnt < byteCount ; intCnt ++ )
5657 {
57- using var binaryWriter = new BinaryWriter ( ms ) ;
58- binaryWriter . Write ( Convert . ToUInt16 ( 0x4d42 ) ) ;
59- binaryWriter . Write ( 54u + colorTableSize + biSizeImage ) ;
60- binaryWriter . Write ( default ( ushort ) ) ;
61- binaryWriter . Write ( default ( ushort ) ) ;
62- binaryWriter . Write ( 54u + colorTableSize ) ;
63- binaryWriter . Write ( bitmapBuffer ) ;
64-
65- using var imageTmp2010 = new Bitmap ( ms ) ;
66- var bytes2010 = ToByteArray ( imageTmp2010 , ImageFormat . Png ) ;
67-
68- return bytes2010 ;
58+ stream . Seek ( thumbInfo . Start , SeekOrigin . Begin ) ;
59+ var udtHeader = new BitmapHeader
60+ {
61+ Size = binaryReader . ReadInt32 ( ) ,
62+ Width = binaryReader . ReadInt32 ( ) ,
63+ Height = binaryReader . ReadInt32 ( ) ,
64+ Planes = binaryReader . ReadInt16 ( ) ,
65+ BitCount = binaryReader . ReadInt16 ( ) ,
66+ Compression = binaryReader . ReadInt32 ( ) ,
67+ SizeImage = binaryReader . ReadInt32 ( ) ,
68+ XPelsPerMeter = binaryReader . ReadInt32 ( ) ,
69+ YPelsPerMeter = binaryReader . ReadInt32 ( ) ,
70+ ClrUsed = binaryReader . ReadInt32 ( ) ,
71+ ClrImportant = binaryReader . ReadInt32 ( ) ,
72+ } ;
73+
74+ var bytBMPBuff = new byte [ thumbInfo . Length + 1 ] ;
75+
76+ if ( udtHeader . BitCount != 8 )
77+ {
78+ continue ;
79+ }
80+
81+ var udtColors = new RgbQuad [ 256 ] ;
82+ for ( int count = 0 ; count < 256 ; count ++ )
83+ {
84+ udtColors [ count ] . Blue = binaryReader . ReadByte ( ) ;
85+ udtColors [ count ] . Green = binaryReader . ReadByte ( ) ;
86+ udtColors [ count ] . Red = binaryReader . ReadByte ( ) ;
87+ udtColors [ count ] . Reserved = binaryReader . ReadByte ( ) ;
88+ }
89+ stream . Seek ( thumbInfo . Start - 1 , SeekOrigin . Begin ) ;
90+
91+ for ( int count = 0 ; count <= thumbInfo . Length ; count ++ )
92+ bytBMPBuff [ count ] = binaryReader . ReadByte ( ) ;
93+
94+ var bmp = new Bitmap ( udtHeader . Width , udtHeader . Height ) ;
95+ var lngCnt = 0 ;
96+
97+ for ( var lngY = 1 ; lngY <= udtHeader . Height ; lngY ++ )
98+ {
99+ for ( var lngX = udtHeader . Width ; lngX >= 1 ; lngX -- )
100+ {
101+ int lngColor = bytBMPBuff [ bytBMPBuff . GetUpperBound ( 0 ) - lngCnt ] ;
102+ var udtColor = udtColors [ lngColor ] ;
103+
104+ var intRed = Convert . ToInt16 ( udtColor . Red ) ;
105+ var intGreen = Convert . ToInt16 ( udtColor . Green ) ;
106+ var intBlue = Convert . ToInt16 ( udtColor . Blue ) ;
107+ lngColor = ColorTranslator . ToOle ( Color . FromArgb ( intRed , intGreen , intBlue ) ) ;
108+
109+ if ( ! RetainBackgroudColor )
110+ {
111+ if ( lngColor == ColorTranslator . ToOle ( ColorBlack ) )
112+ lngColor = ColorTranslator . ToOle ( ColorWhite ) ;
113+ else if ( lngColor == ColorTranslator . ToOle ( ColorWhite ) )
114+ lngColor = ColorTranslator . ToOle ( ColorBlack ) ;
115+ }
116+
117+ bmp . SetPixel ( lngX - 1 , lngY - 1 , ColorTranslator . FromOle ( lngColor ) ) ;
118+ lngCnt ++ ;
119+ }
120+ }
121+
122+ using var outputStream = new MemoryStream ( ) ;
123+ bmp . Save ( outputStream , ImageFormat . Png ) ;
124+ return outputStream . ToArray ( ) ;
69125 }
70126
71- case ThumbnailImageCodes . NULL :
127+ return new byte [ 0 ] ;
128+
129+ case ThumbnailInfo . NullType :
72130 break ; // DWG file doesn't contain a thumbnail
73131 }
74132#pragma warning restore CC0120
@@ -77,18 +135,38 @@ public override byte[] ExtractThumbnailBytes(Stream stream)
77135 return new byte [ 0 ] ;
78136 }
79137
80- public static byte [ ] ToByteArray ( Image image , ImageFormat format )
138+ private struct ThumbnailInfo
139+ {
140+ public const byte BmpType = 2 ;
141+ public const byte PngType = 6 ;
142+ public const byte NullType = 3 ;
143+
144+ public byte Type ;
145+ public int Start ;
146+ public int Length ;
147+ }
148+
149+ private struct BitmapHeader
81150 {
82- using var ms = new MemoryStream ( ) ;
83- image . Save ( ms , format ) ;
84- return ms . ToArray ( ) ;
151+ public int Size ;
152+ public int Width ;
153+ public int Height ;
154+ public short Planes ;
155+ public short BitCount ;
156+ public int Compression ;
157+ public int SizeImage ;
158+ public int XPelsPerMeter ;
159+ public int YPelsPerMeter ;
160+ public int ClrUsed ;
161+ public int ClrImportant ;
85162 }
86163
87- private struct ThumbnailImageCodes
164+ private struct RgbQuad
88165 {
89- internal const byte BMP = 2 ;
90- internal const byte PNG = 6 ;
91- internal const byte NULL = 3 ;
166+ public byte Blue ;
167+ public byte Green ;
168+ public byte Red ;
169+ public byte Reserved ;
92170 }
93171 }
94172}
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