libtiff: Merge branch '16bit_cielab' into 'master'

From f828040e88039a153ac841673f9e0b4c44eb7e6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Caol=C3=A1n=20McNamara?= <[EMAIL REDACTED]>
Date: Mon, 27 Jun 2022 10:19:38 +0000
Subject: [PATCH] Add basic 16bit-cielab support

just a copy of putcontig8bitCIELab that reads 16bit vals but divide l by
257, a and b by 256 before passing to TIFFCIELabToXYZ

motivation: https://bugs.documentfoundation.org/show_bug.cgi?id=131199
the "clavijo16bitlab.tiff" example where tiffinfo says:

Image Width: 2601 Image Length: 3503
Resolution: 96, 96 pixels/inch
Bits/Sample: 16
Compression Scheme: AdobeDeflate
Photometric Interpretation: CIE Lab*
Orientation: row 0 top, col 0 lhs
Samples/Pixel: 3
Rows/Strip: 1
Planar Configuration: single image plane
DateTime: 2020:03:07 10:20:42

---
 libtiff/tif_color.c    | 19 ++++++++++++++++---
 libtiff/tif_getimage.c | 38 ++++++++++++++++++++++++++++++++++----
 libtiff/tiffiop.h      |  2 ++
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/libtiff/tif_color.c b/libtiff/tif_color.c
index 20e41684..e0fc4bf0 100644
--- a/libtiff/tif_color.c
+++ b/libtiff/tif_color.c
@@ -44,7 +44,20 @@ void
 TIFFCIELabToXYZ(TIFFCIELabToRGB *cielab, uint32_t l, int32_t a, int32_t b,
                 float *X, float *Y, float *Z)
 {
-	float L = (float)l * 100.0F / 255.0F;
+	TIFFCIELab16ToXYZ(cielab, l * 257, a * 256, b * 256, X, Y, Z);
+}
+
+/*
+ * For CIELab encoded in 16 bits, L is an unsigned integer range [0,65535].
+ * The a* and b* components are signed integers range [-32768,32767]. The 16
+ * bit chrominance values are encoded as 256 times the 1976 CIE a* and b*
+ * values
+ */
+void
+TIFFCIELab16ToXYZ(TIFFCIELabToRGB *cielab, uint32_t l, int32_t a, int32_t b,
+                  float *X, float *Y, float *Z)
+{
+	float L = (float)l * 100.0F / 65535.0F;
 	float cby, tmp;
 
 	if( L < 8.856F ) {
@@ -55,13 +68,13 @@ TIFFCIELabToXYZ(TIFFCIELabToRGB *cielab, uint32_t l, int32_t a, int32_t b,
 		*Y = cielab->Y0 * cby * cby * cby;
 	}
 
-	tmp = (float)a / 500.0F + cby;
+	tmp = (float)a / 256.0F / 500.0F + cby;
 	if( tmp < 0.2069F )
 		*X = cielab->X0 * (tmp - 0.13793F) / 7.787F;
 	else
 		*X = cielab->X0 * tmp * tmp * tmp;
 
-	tmp = cby - (float)b / 200.0F;
+	tmp = cby - (float)b / 256.0F / 200.0F;
 	if( tmp < 0.2069F )
 		*Z = cielab->Z0 * (tmp - 0.13793F) / 7.787F;
 	else
diff --git a/libtiff/tif_getimage.c b/libtiff/tif_getimage.c
index a1b6570b..7f7fa02b 100644
--- a/libtiff/tif_getimage.c
+++ b/libtiff/tif_getimage.c
@@ -194,7 +194,7 @@ TIFFRGBAImageOK(TIFF* tif, char emsg[1024])
                         }
 			break;
 		case PHOTOMETRIC_CIELAB:
-                        if ( td->td_samplesperpixel != 3 || colorchannels != 3 || td->td_bitspersample != 8 ) {
+                        if ( td->td_samplesperpixel != 3 || colorchannels != 3 || (td->td_bitspersample != 8 && td->td_bitspersample != 16) ) {
                                 sprintf(emsg,
                                         "Sorry, can not handle image with %s=%"PRIu16", %s=%d and %s=%"PRIu16,
                                         "Samples/pixel", td->td_samplesperpixel,
@@ -1784,7 +1784,7 @@ DECLARESepPutFunc(putRGBUAseparate16bittile)
 /*
  * 8-bit packed CIE L*a*b 1976 samples => RGB
  */
-DECLAREContigPutFunc(putcontig8bitCIELab)
+DECLAREContigPutFunc(putcontig8bitCIELab8)
 {
 	float X, Y, Z;
 	uint32_t r, g, b;
@@ -1806,6 +1806,32 @@ DECLAREContigPutFunc(putcontig8bitCIELab)
 	}
 }
 
+/*
+ * 16-bit packed CIE L*a*b 1976 samples => RGB
+ */
+DECLAREContigPutFunc(putcontig8bitCIELab16)
+{
+	float X, Y, Z;
+	uint32_t r, g, b;
+	uint16_t *wp = (uint16_t *)pp;
+	(void) y;
+	fromskew *= 3;
+	for( ; h > 0; --h) {
+		for (x = w; x > 0; --x) {
+			TIFFCIELab16ToXYZ(img->cielab,
+					  (uint16_t)wp[0],
+					  (int16_t)wp[1],
+					  (int16_t)wp[2],
+					  &X, &Y, &Z);
+			TIFFXYZToRGB(img->cielab, X, Y, Z, &r, &g, &b);
+			*cp++ = PACK(r, g, b);
+			wp += 3;
+		}
+		cp += toskew;
+		wp += fromskew;
+	}
+}
+
 /*
  * YCbCr -> RGB conversion and packing routines.
  */
@@ -2395,7 +2421,11 @@ initCIELabConversion(TIFFRGBAImage* img)
 		return NULL;
 	}
 
-	return putcontig8bitCIELab;
+	if (img->bitspersample == 8)
+		return putcontig8bitCIELab8;
+	else if (img->bitspersample == 16)
+		return putcontig8bitCIELab16;
+	return NULL;
 }
 
 /*
@@ -2777,7 +2807,7 @@ PickContigCase(TIFFRGBAImage* img)
 			break;
 		case PHOTOMETRIC_CIELAB:
 			if (img->samplesperpixel == 3 && buildMap(img)) {
-				if (img->bitspersample == 8)
+				if (img->bitspersample == 8 || img->bitspersample == 16)
 					img->put.contig = initCIELabConversion(img);
 				break;
 			}
diff --git a/libtiff/tiffiop.h b/libtiff/tiffiop.h
index e3af461d..7bd50514 100644
--- a/libtiff/tiffiop.h
+++ b/libtiff/tiffiop.h
@@ -429,6 +429,8 @@ extern int TIFFInitZSTD(TIFF*, int);
 extern int TIFFInitWebP(TIFF*, int);
 #endif
 extern const TIFFCodec _TIFFBuiltinCODECS[];
+extern void TIFFCIELab16ToXYZ(TIFFCIELabToRGB *, uint32_t l, int32_t a, int32_t b,
+                              float *, float *, float *);
 
 #if defined(__cplusplus)
 }