StartDecompress Method

Summary

Initializes the buffered decompression engine.

Syntax

Objective-C

C++

Java

public object StartDecompress( 
   CodecsStartDecompressOptions options 
)

Public Function StartDecompress( _ 
   ByVal options As CodecsStartDecompressOptions _ 
) As Object

- (nullable NSObject *)startDecompress:(LTCodecsStartDecompressOptions *)decompressOptions error:(NSError **)error

public Object startDecompress(CodecsStartDecompressOptions options)

public: 
Object^ StartDecompress(  
   CodecsStartDecompressOptions options 
)

Parameters

options
Provides input parameters for the decompression process.

Return Value

An object that identifies the decompression process. This same object must be passed to the Decompress and StopDecompress methods.

Remarks

Initializes the buffered decompression engine. The decompression is then carried out using the Decompress method. It is ended by the StopDecompress method.

Currently, raw JPEG must contain all the Huffman tables encoded. That is, it must be a readable JPEG file.

Example

using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.ImageProcessing; 
using Leadtools.ImageProcessing.Color; 
using Leadtools.Svg; 
 
 
// This sample loads raw data from a PackBits TIF file 
// PackBits.tif is a 24-bit tif packbits compressed file 
// PackBits.tif has 46 strips of packbits data 
// The strip information is obtained by reading the TIF tags TAG_STRIPOFFSETS and TAG_STRIPBYTECOUNTS 
// The strips are directly read and fed to the Compress method 
void LoadRawPackbitsStrips(string packTifFile) 
{ 
	RasterCodecs codecs = new RasterCodecs(); 
 
	string destFileName = Path.Combine(LEAD_VARS.ImagesDir, "Decompress.bmp"); 
 
	CodecsImageInfo imageInfo = codecs.GetInformation(packTifFile, false); 
 
	// StartDecompress 
	CodecsStartDecompressOptions options = CodecsStartDecompressOptions.Empty; 
	options.DataType = CodecsStartDecompressDataType.Strips; 
	options.Format = RasterImageFormat.RawPackBits; 
	options.Width = imageInfo.Width; 
	options.Height = imageInfo.Height; 
	options.BitsPerPixel = imageInfo.BitsPerPixel; 
	options.ViewPerspective = imageInfo.ViewPerspective; 
	options.RawOrder = imageInfo.Order; 
	options.LoadOrder = CodecsLoadByteOrder.BgrOrGray; 
	options.XResolution = imageInfo.XResolution; 
	options.YResolution = imageInfo.YResolution; 
	options.TiffPhotometricInterpretation = CodecsTiffPhotometricInterpretation.Rgb; 
 
	object decompressObject = codecs.StartDecompress(options); 
 
	// Decompress 
 
	const int TAG_STRIPOFFSETS = 0x111; 
	const int TAG_STRIPBYTECOUNTS = 0x117; 
	const int TAG_ROWSPERSTRIP = 0x116; 
	const int MAX_STRIPS = 1000; 
 
	int[] stripOffsets = new int[MAX_STRIPS]; 
	int[] stripSizes = new int[MAX_STRIPS]; 
	int[] rowsPerStripBuffer = new int[1]; 
 
	int maxIndex = ReadTag(codecs, packTifFile, TAG_STRIPOFFSETS, stripOffsets); 
	ReadTag(codecs, packTifFile, TAG_STRIPBYTECOUNTS, stripSizes); 
	ReadTag(codecs, packTifFile, TAG_ROWSPERSTRIP, rowsPerStripBuffer); 
	int rowsPerStrip = rowsPerStripBuffer[0]; 
 
	FileStream fs = File.OpenRead(packTifFile); 
 
	const int row = 0; // Note: this parameter is ignored for strips 
	const int column = 0; // Column offset of tile 
	for (int index = 0; index < maxIndex; index++) 
	{ 
		// seek to the first strip 
		fs.Seek(stripOffsets[index], SeekOrigin.Begin); 
 
		byte[] buffer = new byte[stripSizes[index]]; 
		fs.Read(buffer, 0, buffer.Length); 
 
		// Calculate the height of uncompressed strip/tile 
		int height = rowsPerStrip; 
		if (index == (maxIndex - 1)) 
		{ 
			// fewer rows per strip 
			height = imageInfo.Height - (maxIndex - 1) * rowsPerStrip; 
		} 
 
		codecs.Decompress( 
		   decompressObject, 
		   buffer, 
		   0, 
		   buffer.Length, 
		   imageInfo.Width, 
		   height, 
		   row, 
		   column, 
		   CodecsDecompressDataFlags.Complete); 
	} 
 
	fs.Close(); 
 
	// StopDecompress 
	RasterImage image = codecs.StopDecompress(decompressObject); 
 
	// 'image' contains the uncompressed image 
	codecs.Save(image, destFileName, RasterImageFormat.Bmp, 24); 
	image.Dispose(); 
 
	// Clean up 
	codecs.Dispose(); 
} 
 
// Returns maximum index 
int ReadTag(RasterCodecs codecs, string fileName, int tagId, int[] stripArray) 
{ 
	RasterTagMetadata tag = codecs.ReadTag(fileName, 1, tagId); 
	int[] data = tag.ToInt32(); 
	data.CopyTo(stripArray, 0); 
	return tag.Count; 
} 
 
static class LEAD_VARS 
{ 
   public const string ImagesDir = @"C:\LEADTOOLS21\Resources\Images"; 
}

Requirements

Target Platforms

Reference

RasterCodecs Class

RasterCodecs Members

Compressing and Decompressing Buffers

Speeding Up 1-Bit Documents

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Help Version 21.0.2021.7.2

Leadtools.Codecs Assembly

Introduction

Getting Started

Namespaces

Leadtools.Codecs Namespace

Assemblies