[PATCH 2/3] apps: common: dng_writer: Add thumbnail scanline function for RawXX

[Stefan Klug]

On Thu, Jun 27, 2024 at 02:10:18PM +0100, Kieran Bingham wrote:
> Quoting Stefan Klug (2024-06-27 13:51:10)
> > Add a thumbnail function for raw formats that are 16bit aligned.
> > This is needed for the upcoming RAW10 and RAW12 implemntation.
> > 
> > Use the new function for RAW16 as the thumbScanlineRawXX_CSI2P produces
> > incorrect results for that format (it averages over adjacent bytes,
> > which works for the CSI formats).
> > 
> > Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> > ---
> >  src/apps/common/dng_writer.cpp | 32 ++++++++++++++++++++++++++++----
> >  1 file changed, 28 insertions(+), 4 deletions(-)
> > 
> > diff --git a/src/apps/common/dng_writer.cpp b/src/apps/common/dng_writer.cpp
> > index 88b225d3e099..2cb320ff327b 100644
> > --- a/src/apps/common/dng_writer.cpp
> > +++ b/src/apps/common/dng_writer.cpp
> > @@ -144,6 +144,30 @@ void packScanlineRaw16(void *output, const void *input, unsigned int width)
> >         std::copy(in, in + width, out);
> >  }
> >  
> > +/* Thumbnail function for raw data aligned to 16bit words */
> > +void thumbScanlineRawXX(const FormatInfo &info, void *output,
> 
> Yup, I could still be tempted to call this thumbScanlineRaw ... unless
> ...
> 
> > +                         const void *input, unsigned int width,
> > +                         unsigned int stride)
> > +{
> > +       const uint16_t *in = static_cast<const uint16_t *>(input);
> > +       const uint16_t *in2 = static_cast<const uint16_t *>(input) + stride / 2;
> > +       uint8_t *out = static_cast<uint8_t *>(output);
> > +
> > +       /* shift down to 8 */
> > +       unsigned int shift = info.bitsPerSample - 8;
> > +
> > +       /* simple averaging that produces grey RGB values */
> 
> grey rgb values?

I was looking for the rigt words here. We produce rgb thumbnails, but to
ease the averaging and to prevent the need for debayering only grey is
output. See commit 2223579dfee


> 
> > +       for (unsigned int x = 0; x < width; x++) {
> > +               uint16_t value = (in[0] + in[1] + in2[0] + in2[1]) >> 2;
> > +               value = value >> shift;
> > +               *out++ = value;
> > +               *out++ = value;
> > +               *out++ = value;
> > +               in += 16;
> > +               in2 += 16;
> 
> Does this code work for 8,10,12,14 bit data? Or is the implication that
> it only handled data algined to 16bit (per pixel?) so perhaps that's 10,
> 12, 14, 16?

It only handles formats that are aligned 16bit per pixel (so Raw8 is
excluded) Proposals for a better name are very welcome :-)

Cheers,
Stefan

> 
> 
> 
> > +       }
> > +}
> > +
> >  void packScanlineRaw10_CSI2P(void *output, const void *input, unsigned int width)
> >  {
> >         const uint8_t *in = static_cast<const uint8_t *>(input);
> > @@ -321,25 +345,25 @@ const std::map<PixelFormat, FormatInfo> formatInfo = {
> >                 .bitsPerSample = 16,
> >                 .pattern = { CFAPatternBlue, CFAPatternGreen, CFAPatternGreen, CFAPatternRed },
> >                 .packScanline = packScanlineRaw16,
> > -               .thumbScanline = thumbScanlineRawXX_CSI2P,
> > +               .thumbScanline = thumbScanlineRawXX,
> >         } },
> >         { formats::SGBRG16, {
> >                 .bitsPerSample = 16,
> >                 .pattern = { CFAPatternGreen, CFAPatternBlue, CFAPatternRed, CFAPatternGreen },
> >                 .packScanline = packScanlineRaw16,
> > -               .thumbScanline = thumbScanlineRawXX_CSI2P,
> > +               .thumbScanline = thumbScanlineRawXX,
> >         } },
> >         { formats::SGRBG16, {
> >                 .bitsPerSample = 16,
> >                 .pattern = { CFAPatternGreen, CFAPatternRed, CFAPatternBlue, CFAPatternGreen },
> >                 .packScanline = packScanlineRaw16,
> > -               .thumbScanline = thumbScanlineRawXX_CSI2P,
> > +               .thumbScanline = thumbScanlineRawXX,
> >         } },
> >         { formats::SRGGB16, {
> >                 .bitsPerSample = 16,
> >                 .pattern = { CFAPatternRed, CFAPatternGreen, CFAPatternGreen, CFAPatternBlue },
> >                 .packScanline = packScanlineRaw16,
> > -               .thumbScanline = thumbScanlineRawXX_CSI2P,
> > +               .thumbScanline = thumbScanlineRawXX,
> >         } },
> >         { formats::SBGGR10_CSI2P, {
> >                 .bitsPerSample = 10,
> > -- 
> > 2.43.0
> >