(declarations)

   1 ' PicInfo GIF file information class
   2 ' ©2006 Aivosto Oy (www.aivosto.com)
   3 '
   4 ' This file is part of a sample project for Project Analyzer.
   5 ' Distribution of this file is only allowed along with Project Analyzer
   6 ' according to the Project Analyzer license terms.
   7 
   8 Option Explicit
   9 
  10 Implements IPicInfo
  11 
  12 Private StoredFilename As String ' Filename used in the previous call to ReadFile
  13 
  14 ' FileOK is a flag indicating whether a valid GIF file has been read
  15 ' True - The variables below contain valid data
  16 ' False - The variables below contain undefined data and should not be used
  17 Private FileOK As Boolean
  18 
  19 ' Brief introduction to GIF file structure
  20 '
  21 ' Every GIF file starts with the following bytes:
  22 ' 6 bytes for Signature (either GIF87a or GIF89a in ASCII)
  23 ' 7 bytes for LogicalScreenDescriptor
  24 
  25 Private Signature As String * 6  ' GIF87a, GIF89a
  26 
  27 Private Type TLogicalScreenDescriptor
  28     Width As Integer             ' uint - Width, in pixels
  29     Height As Integer            ' uint - Height, in pixels
  30     Packed As Byte               ' Byte packed with color information

    Type field written, not read: TLogicalScreenDescriptor.BackgroundColorIndex - 0 reads, 1 write
  31     BackgroundColorIndex As Byte ' Background Color index to Global Color Table

    Type field written, not read: TLogicalScreenDescriptor.PixelAspectRatio - 0 reads, 1 write
  32     PixelAspectRatio As Byte     ' Approximation of aspect ratio of pixel in the original image
  33 End Type
  34 Private LogicalScreenDescriptor As TLogicalScreenDescriptor ' Storage for LogicalScreenDescriptor
  35 Private MaxColors As Long        ' Maximum number of colors in .gif
  36