LogicalScreenDescriptor Constructor (logicalScreenSize, hasGlobalColourTable, colourResolution, globalColourTableIsSorted, globalColourTableSizeBits, backgroundColourIndex, pixelAspectRatio)

Constructor.

Declaration Syntax

Visual Basic

Visual C++

public LogicalScreenDescriptor(
	Size logicalScreenSize,
	bool hasGlobalColourTable,
	int colourResolution,
	bool globalColourTableIsSorted,
	int globalColourTableSizeBits,
	int backgroundColourIndex,
	int pixelAspectRatio
)

Public Sub New ( _
	logicalScreenSize As Size, _
	hasGlobalColourTable As Boolean, _
	colourResolution As Integer, _
	globalColourTableIsSorted As Boolean, _
	globalColourTableSizeBits As Integer, _
	backgroundColourIndex As Integer, _
	pixelAspectRatio As Integer _
)

public:
LogicalScreenDescriptor(
	Size logicalScreenSize, 
	bool hasGlobalColourTable, 
	int colourResolution, 
	bool globalColourTableIsSorted, 
	int globalColourTableSizeBits, 
	int backgroundColourIndex, 
	int pixelAspectRatio
)

Parameters

logicalScreenSize (Size): The width and height, in pixels, of the logical screen where the images will be rendered in the displaying device.

hasGlobalColourTable (Boolean): Indicates the presence of a Global Color Table; if the flag is set, the Global Color Table will immediately follow the Logical Screen Descriptor. This flag also selects the interpretation of the Background Color Index; if the flag is set, the value of the Background Color Index field should be used as the table index of the background color.

colourResolution (Int32): The number of bits per primary color available to the original image, minus 1. This value represents the size of the entire palette from which the colors in the graphic were selected, not the number of colors actually used in the graphic. For example, if the value in this field is 3, then the palette of the original image had 4 bits per primary color available to create the image. This value should be set to indicate the richness of the original palette, even if not every color from the whole palette is available on the source machine.

globalColourTableIsSorted (Boolean): Indicates whether the Global Color Table is sorted. If the flag is set, the Global Color Table is sorted, in order of decreasing importance. Typically, the order would be decreasing frequency, with most frequent color first. This assists a decoder, with fewer available colors, in choosing the best subset of colors; the decoder may use an initial segment of the table to render the

globalColourTableSizeBits (Int32): The number of bits required to hold the size of the global colour table. To determine the actual size of the color table, raise 2 to [the value of the field + 1]. E.g. if this parameter is 7 then the global colour table will be 2^(7+1) = 256 bytes long. See also GlobalColourTableSize

backgroundColourIndex (Int32): Gets the index into the Global Color Table for the Background Color. The Background Color is the color used for those pixels on the screen that are not covered by an image. If the Global Color Table Flag is set to (zero), this field should be zero and should be ignored.

pixelAspectRatio (Int32): Gets the factor used to compute an approximation of the aspect ratio of the pixel in the original image.

Return Value

Assembly: GifComponents (Module: GifComponents) Version: 0.1.3594.26453