modules/javafx.graphics/src/main/native-iio/libjpeg7/jfdctfst.c

@@ -1,10 +1,10 @@
 /*
  * jfdctfst.c
  *
  * Copyright (C) 1994-1996, Thomas G. Lane.
- * Modified 2003-2009 by Guido Vollbeding.
+ * Modified 2003-2017 by Guido Vollbeding.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains a fast, not so accurate integer implementation of the
  * forward DCT (Discrete Cosine Transform).

@@ -42,11 +42,11 @@
 /*
  * This module is specialized to the case DCTSIZE = 8.
  */
 
 #if DCTSIZE != 8
-  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
+  Sorry, this code only copes with 8x8 DCT blocks. /* deliberate syntax err */
 #endif
 
 
 /* Scaling decisions are generally the same as in the LL&M algorithm;
  * see jfdctint.c for more details.  However, we choose to descale

@@ -107,10 +107,12 @@
 #define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
 
 
 /*
  * Perform the forward DCT on one block of samples.
+ *
+ * cK represents cos(K*pi/16).
  */
 
 GLOBAL(void)
 jpeg_fdct_ifast (DCTELEM * data, JSAMPARRAY sample_data, JDIMENSION start_col)
 {

@@ -143,11 +145,11 @@
     tmp10 = tmp0 + tmp3;        /* phase 2 */
     tmp13 = tmp0 - tmp3;
     tmp11 = tmp1 + tmp2;
     tmp12 = tmp1 - tmp2;
 
-    /* Apply unsigned->signed conversion */
+    /* Apply unsigned->signed conversion. */
     dataptr[0] = tmp10 + tmp11 - 8 * CENTERJSAMPLE; /* phase 3 */
     dataptr[4] = tmp10 - tmp11;
 
     z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */
     dataptr[2] = tmp13 + z1;    /* phase 5 */