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

[Stefan Klug]

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,
+			  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 */
+	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;
+	}
+}
+
 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