JPEG Extract DCT Tablas

Question

Estoy desarrollando un visor / editor de imágenes usando VS2008, MFC y WIC y me gustaría recomendar a JPEG tan cerca (Wize de calidad) posible a su original, después del procesamiento de la imagen.¿Alguien sabe cómo extraer las tablas de luminancia y crominancia para establecer en
http://msdn.microsoft.com/en-US / Library / GG430026% 28V= vs.85% 29.aspx sin Tener que usar una biblioteca grande adicional (como libjpeg)?

Answer 1

The JPEG standard specification covers the details of the luminance and chrominance table.

In JPEG terminology, those tables are both referred to as "quantization table" (DQT). The luminance quantization table is applied on the "Y" channel and the chrominance quantization table is applied to "Cb" and "Cr" channels.

This website lists the quantization tables for a large number of camera manufacturers and JPEG authoring software.

To recompress an image using the same quantization tables as another existing image:

• Query and enumerate all IWICMetadataBlockReader objects from the source image (IWICBitmapFrameDecode).
• Find the metadata blocks which have the types GUID_MetadataFormatJpegChrominance and GUID_MetadataFormatJpegLuminance
• Extract their binary data, and use those data to initialize the Luminance and Chrominance properties of the JPEG encoder options by putting them into the IPropertyBag when calling IWICBitmapFrameEncode::Initialize.