[LIBJPEG]

[reactos.git] / reactos / dll / 3rdparty / libjpeg / jidctflt.c

diff --git a/reactos/dll/3rdparty/libjpeg/jidctflt.c b/reactos/dll/3rdparty/libjpeg/jidctflt.c
index 23ae9d3..c7e832a 100644 (file)
--- a/reactos/dll/3rdparty/libjpeg/jidctflt.c
+++ b/reactos/dll/3rdparty/libjpeg/jidctflt.c
@@ -2,7 +2,7 @@
  * jidctflt.c
  *
  * Copyright (C) 1994-1998, Thomas G. Lane.
- * Modified 2010 by Guido Vollbeding.
+ * Modified 2010-2015 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.
  *
@@ -63,6 +63,8 @@
 
 /*
  * Perform dequantization and inverse DCT on one block of coefficients.
+ *
+ * cK represents cos(K*pi/16).
  */
 
 GLOBAL(void)
@@ -77,7 +79,7 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
   FLOAT_MULT_TYPE * quantptr;
   FAST_FLOAT * wsptr;
   JSAMPROW outptr;
-  JSAMPLE *range_limit = cinfo->sample_range_limit;
+  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
   int ctr;
   FAST_FLOAT workspace[DCTSIZE2]; /* buffers data between passes */
 
@@ -95,14 +97,14 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
      * With typical images and quantization tables, half or more of the
      * column DCT calculations can be simplified this way.
      */
-    
+
     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
        inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
        inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
        inptr[DCTSIZE*7] == 0) {
       /* AC terms all zero */
       FAST_FLOAT dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
-      
+
       wsptr[DCTSIZE*0] = dcval;
       wsptr[DCTSIZE*1] = dcval;
       wsptr[DCTSIZE*2] = dcval;
@@ -111,13 +113,13 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
       wsptr[DCTSIZE*5] = dcval;
       wsptr[DCTSIZE*6] = dcval;
       wsptr[DCTSIZE*7] = dcval;
-      
+
       inptr++;                 /* advance pointers to next column */
       quantptr++;
       wsptr++;
       continue;
     }
-    
+
     /* Even part */
 
     tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
@@ -135,7 +137,7 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     tmp3 = tmp10 - tmp13;
     tmp1 = tmp11 + tmp12;
     tmp2 = tmp11 - tmp12;
-    
+
     /* Odd part */
 
     tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
@@ -172,7 +174,7 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     quantptr++;
     wsptr++;
   }
-  
+
   /* Pass 2: process rows from work array, store into output array. */
 
   wsptr = workspace;
@@ -183,16 +185,17 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
      * the simplification applies less often (typically 5% to 10% of the time).
      * And testing floats for zero is relatively expensive, so we don't bother.
      */
-    
+
     /* Even part */
 
-    /* Apply signed->unsigned and prepare float->int conversion */
-    z5 = wsptr[0] + ((FAST_FLOAT) CENTERJSAMPLE + (FAST_FLOAT) 0.5);
+    /* Prepare range-limit and float->int conversion */
+    z5 = wsptr[0] + (((FAST_FLOAT) RANGE_CENTER) + ((FAST_FLOAT) 0.5));
     tmp10 = z5 + wsptr[4];
     tmp11 = z5 - wsptr[4];
 
     tmp13 = wsptr[2] + wsptr[6];
-    tmp12 = (wsptr[2] - wsptr[6]) * ((FAST_FLOAT) 1.414213562) - tmp13;
+    tmp12 = (wsptr[2] - wsptr[6]) *
+             ((FAST_FLOAT) 1.414213562) - tmp13; /* 2*c4 */
 
     tmp0 = tmp10 + tmp13;
     tmp3 = tmp10 - tmp13;
@@ -206,28 +209,28 @@ jpeg_idct_float (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     z11 = wsptr[1] + wsptr[7];
     z12 = wsptr[1] - wsptr[7];
 
-    tmp7 = z11 + z13;
-    tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562);
+    tmp7 = z11 + z13;          /* phase 5 */
+    tmp11 = (z11 - z13) * ((FAST_FLOAT) 1.414213562); /* 2*c4 */
 
     z5 = (z10 + z12) * ((FAST_FLOAT) 1.847759065); /* 2*c2 */
     tmp10 = z5 - z12 * ((FAST_FLOAT) 1.082392200); /* 2*(c2-c6) */
     tmp12 = z5 - z10 * ((FAST_FLOAT) 2.613125930); /* 2*(c2+c6) */
 
-    tmp6 = tmp12 - tmp7;
+    tmp6 = tmp12 - tmp7;       /* phase 2 */
     tmp5 = tmp11 - tmp6;
     tmp4 = tmp10 - tmp5;
 
     /* Final output stage: float->int conversion and range-limit */
 
-    outptr[0] = range_limit[((int) (tmp0 + tmp7)) & RANGE_MASK];
-    outptr[7] = range_limit[((int) (tmp0 - tmp7)) & RANGE_MASK];
-    outptr[1] = range_limit[((int) (tmp1 + tmp6)) & RANGE_MASK];
-    outptr[6] = range_limit[((int) (tmp1 - tmp6)) & RANGE_MASK];
-    outptr[2] = range_limit[((int) (tmp2 + tmp5)) & RANGE_MASK];
-    outptr[5] = range_limit[((int) (tmp2 - tmp5)) & RANGE_MASK];
-    outptr[3] = range_limit[((int) (tmp3 + tmp4)) & RANGE_MASK];
-    outptr[4] = range_limit[((int) (tmp3 - tmp4)) & RANGE_MASK];
-    
+    outptr[0] = range_limit[(int) (tmp0 + tmp7) & RANGE_MASK];
+    outptr[7] = range_limit[(int) (tmp0 - tmp7) & RANGE_MASK];
+    outptr[1] = range_limit[(int) (tmp1 + tmp6) & RANGE_MASK];
+    outptr[6] = range_limit[(int) (tmp1 - tmp6) & RANGE_MASK];
+    outptr[2] = range_limit[(int) (tmp2 + tmp5) & RANGE_MASK];
+    outptr[5] = range_limit[(int) (tmp2 - tmp5) & RANGE_MASK];
+    outptr[3] = range_limit[(int) (tmp3 + tmp4) & RANGE_MASK];
+    outptr[4] = range_limit[(int) (tmp3 - tmp4) & RANGE_MASK];
+
     wsptr += DCTSIZE;          /* advance pointer to next row */
   }
 }