org.apache.shindig.gadgets.rewrite.image

Class JpegImageUtils.JpegImageParams

java.lang.Object

org.apache.shindig.gadgets.rewrite.image.JpegImageUtils.JpegImageParams

Enclosing class:

JpegImageUtils

public static class JpegImageUtils.JpegImageParams
extends Object

Method Summary

Methods

Modifier and Type	Method and Description
void	addQTable(int tableIndex, int[] table) Adds quantization table to image data.
float	approximateQuality(int[] table, int[] stdTable) Quality is defined in terms of the base quantization tables used by encoder.
float	getApproxQualityFactor()
float	getChromaQualityFactor()
float	getLumaQualityFactor()
JpegImageUtils.SamplingModes	getSamplingMode()
boolean	isHuffmanOptimized()
void	setChromaIndex(int index)
void	setHuffmanOptimized(boolean huffmanOptimized)
void	setLumaIndex(int index)
void	setSamplingMode(int samplingMode)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getSamplingMode

public JpegImageUtils.SamplingModes getSamplingMode()

setSamplingMode

public void setSamplingMode(int samplingMode)

isHuffmanOptimized

public boolean isHuffmanOptimized()

setHuffmanOptimized

public void setHuffmanOptimized(boolean huffmanOptimized)

setLumaIndex

public void setLumaIndex(int index)

setChromaIndex

public void setChromaIndex(int index)

approximateQuality

public float approximateQuality(int[] table,
                       int[] stdTable)

Quality is defined in terms of the base quantization tables used by encoder. Q = quant table, q = compression quality and S = table used by encoder, Encoder does the following. if q > 0.5 then Q = 2 - 2*q*S otherwise Q = (0.5/q)*S. Since we dont have access to the table used by encoder. But it is generally close to the standard table defined by JPEG. Hence, we approx by taking sum of all values of the standard JPEG table and comparing with sum of all values of quant table.

Parameters:

table - quantization table specified in the jpeg header.

stdTable - reference quantization table specified in jpeg standard.

Returns:

approximate compression quality which lies in interval [0.0, 1.0].

addQTable

public void addQTable(int tableIndex,
             int[] table)

Adds quantization table to image data.

Parameters:

tableIndex - quantization table index.

table - quantization table that is used in while encoding.

getChromaQualityFactor

public float getChromaQualityFactor()

getLumaQualityFactor

public float getLumaQualityFactor()

getApproxQualityFactor

public float getApproxQualityFactor()