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