C# Class BitMiracle.LibJpeg.Classic.Internal.my_upsampler

Initialize for an upsampling pass.

Control routine to do upsampling (and color conversion). In this version we upsample each component independently. We upsample one row group into the conversion buffer, then apply color conversion a row at a time.

For full-size components, we just make color_buf[ci] point at the input buffer, and thus avoid copying any data. Note that this is safe only because sep_upsample doesn't declare the input row group "consumed" until we are done color converting and emitting it.

Fast processing for the common case of 2:1 horizontal and 1:1 vertical. It's still a box filter.

Fast processing for the common case of 2:1 horizontal and 2:1 vertical. It's still a box filter.

This version handles any integral sampling ratios. This is not used for typical JPEG files, so it need not be fast. Nor, for that matter, is it particularly accurate: the algorithm is simple replication of the input pixel onto the corresponding output pixels. The hi-falutin sampling literature refers to this as a "box filter". A box filter tends to introduce visible artifacts, so if you are actually going to use 3:1 or 4:1 sampling ratios you would be well advised to improve this code.

This is a no-op version used for "uninteresting" components. These components will not be referenced by color conversion.