Add support for decoding to 565 to libjpeg_turbo

jdcolor.c

Index: jdcolor.c
diff --git a/jdcolor.c b/jdcolor.c
index ccf9047911120dd2dde2b45e9626727fcbf1f4c7..2c68ed83b7d7f2eff1f079296f778f1516095058 100644
--- a/jdcolor.c
+++ b/jdcolor.c
@@ -6,7 +6,8 @@
  * Modified 2011 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2009, 2011-2012, D. R. Commander.
+ * Copyright (C) 2009, 2011-2012, 2014, D. R. Commander.
+ * Copyright (C) 2013, Linaro Limited.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains output colorspace conversion routines.
@@ -544,6 +545,164 @@ ycck_cmyk_convert (j_decompress_ptr cinfo,
 
 
 /*
+ * RGB565 conversion
+ */
+
+#define PACK_SHORT_565_LE(r, g, b)   ((((r) << 8) & 0xF800) |  \
+                                      (((g) << 3) & 0x7E0) | ((b) >> 3))
+#define PACK_SHORT_565_BE(r, g, b)   (((r) & 0xF8) | ((g) >> 5) |  \
+                                      (((g) << 11) & 0xE000) |  \
+                                      (((b) << 5) & 0x1F00))
+
+#define PACK_TWO_PIXELS_LE(l, r)     ((r << 16) | l)
+#define PACK_TWO_PIXELS_BE(l, r)     ((l << 16) | r)
+
+#define PACK_NEED_ALIGNMENT(ptr)     (((size_t)(ptr)) & 3)
+
+#define WRITE_TWO_ALIGNED_PIXELS(addr, pixels)  ((*(int *)(addr)) = pixels)
+
+#define DITHER_565_R(r, dither)  ((r) + ((dither) & 0xFF))
+#define DITHER_565_G(g, dither)  ((g) + (((dither) & 0xFF) >> 1))
+#define DITHER_565_B(b, dither)  ((b) + ((dither) & 0xFF))
+
+
+/* Declarations for ordered dithering
+ *
+ * We use a 4x4 ordered dither array packed into 32 bits.  This array is
+ * sufficent for dithering RGB888 to RGB565.
+ */
+
+#define DITHER_MASK       0x3
+#define DITHER_ROTATE(x)  (((x) << 24) | (((x) >> 8) & 0x00FFFFFF))
+static const INT32 dither_matrix[4] = {
+  0x0008020A,
+  0x0C040E06,
+  0x030B0109,
+  0x0F070D05
+};
+
+
+static INLINE boolean is_big_endian(void)
+{
+  int test_value = 1;
+  if(*(char *)&test_value != 1)
+    return TRUE;
+  return FALSE;
+}
+
+
+/* Include inline routines for RGB565 conversion */
+
+#define PACK_SHORT_565 PACK_SHORT_565_LE
+#define PACK_TWO_PIXELS PACK_TWO_PIXELS_LE
+#define ycc_rgb565_convert_internal ycc_rgb565_convert_le
+#define ycc_rgb565D_convert_internal ycc_rgb565D_convert_le
+#define rgb_rgb565_convert_internal rgb_rgb565_convert_le
+#define rgb_rgb565D_convert_internal rgb_rgb565D_convert_le
+#define gray_rgb565_convert_internal gray_rgb565_convert_le
+#define gray_rgb565D_convert_internal gray_rgb565D_convert_le
+#include "jdcol565.c"
+#undef PACK_SHORT_565
+#undef PACK_TWO_PIXELS
+#undef ycc_rgb565_convert_internal
+#undef ycc_rgb565D_convert_internal
+#undef rgb_rgb565_convert_internal
+#undef rgb_rgb565D_convert_internal
+#undef gray_rgb565_convert_internal
+#undef gray_rgb565D_convert_internal
+
+#define PACK_SHORT_565 PACK_SHORT_565_BE
+#define PACK_TWO_PIXELS PACK_TWO_PIXELS_BE
+#define ycc_rgb565_convert_internal ycc_rgb565_convert_be
+#define ycc_rgb565D_convert_internal ycc_rgb565D_convert_be
+#define rgb_rgb565_convert_internal rgb_rgb565_convert_be
+#define rgb_rgb565D_convert_internal rgb_rgb565D_convert_be
+#define gray_rgb565_convert_internal gray_rgb565_convert_be
+#define gray_rgb565D_convert_internal gray_rgb565D_convert_be
+#include "jdcol565.c"
+#undef PACK_SHORT_565
+#undef PACK_TWO_PIXELS
+#undef ycc_rgb565_convert_internal
+#undef ycc_rgb565D_convert_internal
+#undef rgb_rgb565_convert_internal
+#undef rgb_rgb565D_convert_internal
+#undef gray_rgb565_convert_internal
+#undef gray_rgb565D_convert_internal
+
+
+METHODDEF(void)
+ycc_rgb565_convert (j_decompress_ptr cinfo,
+                    JSAMPIMAGE input_buf, JDIMENSION input_row,
+                    JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    ycc_rgb565_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    ycc_rgb565_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+METHODDEF(void)
+ycc_rgb565D_convert (j_decompress_ptr cinfo,
+                     JSAMPIMAGE input_buf, JDIMENSION input_row,
+                     JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    ycc_rgb565D_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    ycc_rgb565D_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+METHODDEF(void)
+rgb_rgb565_convert (j_decompress_ptr cinfo,
+                    JSAMPIMAGE input_buf, JDIMENSION input_row,
+                    JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    rgb_rgb565_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    rgb_rgb565_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+METHODDEF(void)
+rgb_rgb565D_convert (j_decompress_ptr cinfo,
+                     JSAMPIMAGE input_buf, JDIMENSION input_row,
+                     JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    rgb_rgb565D_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    rgb_rgb565D_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+METHODDEF(void)
+gray_rgb565_convert (j_decompress_ptr cinfo,
+                     JSAMPIMAGE input_buf, JDIMENSION input_row,
+                     JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    gray_rgb565_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    gray_rgb565_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+METHODDEF(void)
+gray_rgb565D_convert (j_decompress_ptr cinfo,
+                      JSAMPIMAGE input_buf, JDIMENSION input_row,
+                      JSAMPARRAY output_buf, int num_rows)
+{
+  if (is_big_endian())
+    gray_rgb565D_convert_be(cinfo, input_buf, input_row, output_buf, num_rows);
+  else
+    gray_rgb565D_convert_le(cinfo, input_buf, input_row, output_buf, num_rows);
+}
+
+
+/*
  * Empty method for start_pass.
  */
 
@@ -649,7 +808,37 @@ jinit_color_deconverter (j_decompress_ptr cinfo)
       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
     break;
 
-  case JCS_CMYK:
+  case JCS_RGB565:
+    cinfo->out_color_components = 3;
+    if (cinfo->dither_mode == JDITHER_NONE) {
+      if (cinfo->jpeg_color_space == JCS_YCbCr) {
+        if (jsimd_can_ycc_rgb565())
+          cconvert->pub.color_convert = jsimd_ycc_rgb565_convert;
+        else {
+          cconvert->pub.color_convert = ycc_rgb565_convert;
+          build_ycc_rgb_table(cinfo);
+        }
+      } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
+        cconvert->pub.color_convert = gray_rgb565_convert;
+      } else if (cinfo->jpeg_color_space == JCS_RGB) {
+        cconvert->pub.color_convert = rgb_rgb565_convert;
+      } else
+        ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
+    } else {
+      /* only ordered dithering is supported */
+      if (cinfo->jpeg_color_space == JCS_YCbCr) {
+        cconvert->pub.color_convert = ycc_rgb565D_convert;
+        build_ycc_rgb_table(cinfo);
+      } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
+        cconvert->pub.color_convert = gray_rgb565D_convert;
+      } else if (cinfo->jpeg_color_space == JCS_RGB) {
+        cconvert->pub.color_convert = rgb_rgb565D_convert;
+      } else
+        ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
+    }
+    break;
+
+case JCS_CMYK:
     cinfo->out_color_components = 4;
     if (cinfo->jpeg_color_space == JCS_YCCK) {
       cconvert->pub.color_convert = ycck_cmyk_convert;