diff --git a/ChangeLog.txt b/ChangeLog.txt
index 885a3268..5e05a384 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -22,6 +22,11 @@ See the comments in Makefile.am for information on how to re-enable the tests
 and to specify an expected result for them based on the particulars of your
 platform.
 
+[4] The NULL color conversion routines have been significantly optimized,
+which speeds up the compression of RGB and CMYK JPEGs by 5-20% when using
+64-bit code and 0-3% when using 32-bit code, and the decompression of those
+images by 10-30% when using 64-bit code and 3-12% when using 32-bit code.
+
 
 1.4.0
 =====
diff --git a/jccolor.c b/jccolor.c
index 4be75f71..34ea23b8 100644
--- a/jccolor.c
+++ b/jccolor.c
@@ -5,7 +5,7 @@
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2009-2012, D. R. Commander.
+ * Copyright (C) 2009-2012, 2015 D. R. Commander.
  * Copyright (C) 2014, MIPS Technologies, Inc., California
  * For conditions of distribution and use, see the accompanying README file.
  *
@@ -464,24 +464,54 @@ null_convert (j_compress_ptr cinfo,
               JDIMENSION output_row, int num_rows)
 {
   register JSAMPROW inptr;
-  register JSAMPROW outptr;
+  register JSAMPROW outptr, outptr0, outptr1, outptr2, outptr3;
   register JDIMENSION col;
   register int ci;
   int nc = cinfo->num_components;
   JDIMENSION num_cols = cinfo->image_width;
 
-  while (--num_rows >= 0) {
-    /* It seems fastest to make a separate pass for each component. */
-    for (ci = 0; ci < nc; ci++) {
-      inptr = *input_buf;
-      outptr = output_buf[ci][output_row];
+  if (nc == 3) {
+    while (--num_rows >= 0) {
+      inptr = *input_buf++;
+      outptr0 = output_buf[0][output_row];
+      outptr1 = output_buf[1][output_row];
+      outptr2 = output_buf[2][output_row];
+      output_row++;
       for (col = 0; col < num_cols; col++) {
-        outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
-        inptr += nc;
+        outptr0[col] = *inptr++;
+        outptr1[col] = *inptr++;
+        outptr2[col] = *inptr++;
       }
     }
-    input_buf++;
-    output_row++;
+  } else if (nc == 4) {
+    while (--num_rows >= 0) {
+      inptr = *input_buf++;
+      outptr0 = output_buf[0][output_row];
+      outptr1 = output_buf[1][output_row];
+      outptr2 = output_buf[2][output_row];
+      outptr3 = output_buf[3][output_row];
+      output_row++;
+      for (col = 0; col < num_cols; col++) {
+        outptr0[col] = *inptr++;
+        outptr1[col] = *inptr++;
+        outptr2[col] = *inptr++;
+        outptr3[col] = *inptr++;
+      }
+    }
+  } else {
+    while (--num_rows >= 0) {
+      /* It seems fastest to make a separate pass for each component. */
+      for (ci = 0; ci < nc; ci++) {
+        inptr = *input_buf;
+        outptr = output_buf[ci][output_row];
+        for (col = 0; col < num_cols; col++) {
+          outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
+          inptr += nc;
+        }
+      }
+      input_buf++;
+      output_row++;
+    }
   }
 }
 
diff --git a/jdcolor.c b/jdcolor.c
index 779fa51f..38db90f2 100644
--- a/jdcolor.c
+++ b/jdcolor.c
@@ -6,7 +6,7 @@
  * Modified 2011 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2009, 2011-2012, 2014, D. R. Commander.
+ * Copyright (C) 2009, 2011-2012, 2014-2015, D. R. Commander.
  * Copyright (C) 2013, Linaro Limited.
  * For conditions of distribution and use, see the accompanying README file.
  *
@@ -364,23 +364,53 @@ null_convert (j_decompress_ptr cinfo,
               JSAMPIMAGE input_buf, JDIMENSION input_row,
               JSAMPARRAY output_buf, int num_rows)
 {
-  register JSAMPROW inptr, outptr;
-  register JDIMENSION count;
+  register JSAMPROW inptr, inptr0, inptr1, inptr2, inptr3, outptr;
+  register JDIMENSION col;
   register int num_components = cinfo->num_components;
   JDIMENSION num_cols = cinfo->output_width;
   int ci;
 
-  while (--num_rows >= 0) {
-    for (ci = 0; ci < num_components; ci++) {
-      inptr = input_buf[ci][input_row];
-      outptr = output_buf[0] + ci;
-      for (count = num_cols; count > 0; count--) {
-        *outptr = *inptr++;     /* needn't bother with GETJSAMPLE() here */
-        outptr += num_components;
+  if (num_components == 3) {
+    while (--num_rows >= 0) {
+      inptr0 = input_buf[0][input_row];
+      inptr1 = input_buf[1][input_row];
+      inptr2 = input_buf[2][input_row];
+      input_row++;
+      outptr = *output_buf++;
+      for (col = 0; col < num_cols; col++) {
+        *outptr++ = inptr0[col];
+        *outptr++ = inptr1[col];
+        *outptr++ = inptr2[col];
       }
     }
-    input_row++;
-    output_buf++;
+  } else if (num_components == 4) {
+    while (--num_rows >= 0) {
+      inptr0 = input_buf[0][input_row];
+      inptr1 = input_buf[1][input_row];
+      inptr2 = input_buf[2][input_row];
+      inptr3 = input_buf[3][input_row];
+      input_row++;
+      outptr = *output_buf++;
+      for (col = 0; col < num_cols; col++) {
+        *outptr++ = inptr0[col];
+        *outptr++ = inptr1[col];
+        *outptr++ = inptr2[col];
+        *outptr++ = inptr3[col];
+      }
+    }
+  } else {
+    while (--num_rows >= 0) {
+      for (ci = 0; ci < num_components; ci++) {
+        inptr = input_buf[ci][input_row];
+        outptr = *output_buf;
+        for (col = 0; col < num_cols; col++) {
+          outptr[ci] = inptr[col];
+          outptr += num_components;
+        }
+      }
+      output_buf++;
+      input_row++;
+    }
   }
 }