QualityFactor Property Bag Item

The quality factor is a number that determines the degree of loss in the compression process for lossy formats. The following LEAD encoders support the QualityFactor property bag item:

LEAD Encoder CLSID	Valid QualityFactor values
CLSID_WICLeadAbcEncoder	One of the WICLeadAbcQualityFactorPredefined enumeration values.
CLSID_WICLeadCmpEncoder	One of the WICLeadCmpQualityFactorPredefined enumeration values, or 2 through 255
CLSID_WICLeadCmwEncoder	2 through 255
CLSID_WICLeadDicomEncoder	Depends on the subformat being used. See remarks below.
CLSID_WICLeadIcoEncoder	Depends on the subformat being used. See remarks below.
CLSID_WICLeadHdpEncoder	1 through 255
CLSID_WICLeadJpegEncoder	0 (lossless) or 2 through 255
CLSID_WICLeadJ2kEncoder	-1(lossless), 0(lossless), 1 through 255
CLSID_WICLeadMngEncoder	2 through 255
CLSID_WICLeadPdfEncoder	Depends on the subformat being used. See remarks below.
CLSID_WICLeadPngEncoder	0 through 9
CLSID_WICLeadTiffEncoder	Depends on the subformat being used. See remarks below.
CLSID_WICLeadXpsEncoder	Depends on the subformat being used. See remarks below.

Typically, a lower quality factor results in higher quality and larger files. A higher quality factor results in smaller but lower quality files. Different LEAD Bitmap Encoders have different valid quality factor ranges. For example, the LEAD Jpeg Bitmap Encoder supports a quality factor in the range from 2 through 255 inclusive. But the LEAD Png Bitmap Encoder supports a quality factor in the range of 0 through 9 inclusive.

In addition to a quality factor range, some LEAD Bitmap Encoders support predefined quality factors. For example the LEAD Cmp Bitmap Encoder supports a quality factor range of 2 through 255, and also the predefined quality factors in theWICLeadCmpQualityFactorPredefined enumeration. For more information, refer to the IWICLeadBitmapEncoder::GetQualityFactorPredefined method and the IWICLeadBitmapEncoder::GetQualityFactorPredefinedFriendlyName method.

Certain LEAD Bitmap Encoders can store image data in more than one subformat. For example, the LEAD Xps Bitmap Encoder supports JPEG compression (with a quality factor range of 2 -255) or PNG compression (with a quality factor range of 0-9). So the SubFormat property of a LEAD Bitmap Encoder can affect the valid quality factor range. To get the quality factor range for a LEAD Bitmap Encoder, call the IWICLeadBitmapEncoder::GetQualityFactorRange method. The tables below show the QualityFactor ranges for these encoders.

To determine if a LEAD Bitmap Encoder supports the QualityFactor property, call the IWICLeadBitmapEncoder::GetSubFormatFlags method.

CLSID_WICLeadDicomEncoder

SubFormat	QualityFactor Values
WICLeadSubFormatDicomJpegGray	0(lossless), 2 through 255
WICLeadSubFormatDicomJ2kGray	0(lossless), 2 through 255
WICLeadSubFormatDicomJpegColor	0(lossless), 2 through 255
All other SubFormats	Ignored

CLSID_WICLeadTiffEncoder

SubFormat	QualityFactor Values
WICLeadSubFormatTifAbc	One of the WICLeadAbcQualityFactorPredefined enumeration values.
WICLeadSubFormatTifJpeg	0(lossless), 2 through 255
WICLeadSubFormatTifJpeg411	0(lossless), 2 through 255
WICLeadSubFormatTifJpeg422	0(lossless), 2 through 255
WICLeadSubFormatTifCmp	One of the WICLeadCmpQualityFactorPredefined enumeration values, or 2 through 255
WICLeadSubFormatTifJ2k	-1(lossless), 0(lossless), 1 through 255
WICLeadSubFormatTifCmw	2 through 255
All other SubFormats	Ignored

CLSID_WICLeadPdfEncoder

SubFormat	QualityFactor Values
WICLeadSubFormatRasPdfLzw	2 through 255
WICLeadSubFormatRasPdfJpeg	0(lossless), 2 through 255
WICLeadSubFormatRasPdfJpeg422	0(lossless), 2 through 255
WICLeadSubFormatRasPdfJpeg411	0(lossless), 2 through 255
WICLeadSubFormatRasPdfLzwCmyk	2 through 255
All other SubFormats	Ignored

CLSID_WICLeadXpsEncoder

SubFormat	QualityFactor Values
WICLeadSubFormatXps	0 through 9
WICLeadSubFormatXpsJpeg	0(lossless), 2 through 255
WICLeadSubFormatXpsJpeg422	0(lossless), 2 through 255
WICLeadSubFormatXpsJpeg411	0(lossless), 2 through 255

CLSID_WICLeadIcoEncoder

SubFormat	QualityFactor Values
WICLeadSubFormatPngIco	0 through 9
WICLeadSubFormatTifJpeg	0(lossless), 2 through 255
WICLeadSubFormatWinIco	Ignored

References

LEAD WIC-Enabled Codecs Overview
Registering a LEAD WIC-Enabled Codec
LEAD Bitmap Encoder Property Bag
LEAD Bitmap Encoder Property Bag: Jpeg2000 Specific Options
LEAD Bitmap Encoder Property Bag: Jbig2 Specific Options
LEAD Bitmap Encoder Property Bag: XPS Specific Options