[libpng16] Eliminated Intel icc/icl compiler warnings. The Intel (GCC derived)

compiler issues slightly different warnings from those issued by the
current vesions of GCC. This eliminates those warnings by
adding/removing casts and small code rewrites.

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.6.0beta07 - January 24, 2012
+Libpng 1.6.0beta07 - January 25, 2012
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -118,7 +118,11 @@ Version 1.6.0beta06 [January 24, 2012]
     review; the documentation has not yet been updated.
   Fixed Min/GW uninstall to remove libpng.dll.a
 
-Version 1.6.0beta07 [January 24, 2012]
+Version 1.6.0beta07 [January 25, 2012]
+  Eliminated Intel icc/icl compiler warnings. The Intel (GCC derived)
+    compiler issues slightly different warnings from those issued by the
+    current vesions of GCC. This eliminates those warnings by
+    adding/removing casts and small code rewrites.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -3869,7 +3869,11 @@ Version 1.6.0beta06 [January 24, 2012]
     review; the documentation has not yet been updated.
   Fixed Min/GW uninstall to remove libpng.dll.a
 
-Version 1.6.0beta07 [January 24, 2012]
+Version 1.6.0beta07 [January 25, 2012]
+  Eliminated Intel icc/icl compiler warnings. The Intel (GCC derived)
+    compiler issues slightly different warnings from those issued by the
+    current vesions of GCC. This eliminates those warnings by
+    adding/removing casts and small code rewrites.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

contrib/libtests/pngstest.c

@@ -1530,7 +1530,10 @@ compare_two_images(Image *a, Image *b, int via_linear)
       png_byte bstart = 0;
 
       /* Set to the actual number of channels in 'a' */
-      channels = (formata & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
+      if (formata & PNG_FORMAT_FLAG_COLOR)
+         channels = 3U;
+      else
+         channels = 1U;
 
       if (formata & PNG_FORMAT_FLAG_ALPHA)
       {
@@ -2282,7 +2285,7 @@ testimage(Image *image, png_uint_32 opts, format_list *pf)
 }
 
 int
-main(int argc, const char **argv)
+main(int argc, char **argv)
 {
    png_uint_32 opts = 0;
    format_list formats;

contrib/libtests/pngvalid.c

@@ -2903,9 +2903,9 @@ make_standard_palette(png_store* ps, int npalette, int do_tRNS)
     */
    for (; i<8; ++i)
    {
-      values[i][1] = (i&1) ? 255 : 0;
+      values[i][1] = (png_byte)((i&1) ? 255U : 0U);
-      values[i][2] = (i&2) ? 255 : 0;
+      values[i][2] = (png_byte)((i&2) ? 255U : 0U);
-      values[i][3] = (i&4) ? 255 : 0;
+      values[i][3] = (png_byte)((i&4) ? 255U : 0U);
    }
 
    /* Then add 62 grays (one quarter of the remaining 256 slots). */
@@ -3166,20 +3166,20 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
    switch (bit_size(pp, colour_type, bit_depth))
    {
       case 1:
-         while (i<128/8) buffer[i] = v & 0xff, v += 17, ++i;
+         while (i<128/8) buffer[i] = (png_byte)(v & 0xff), v += 17, ++i;
          return;
 
       case 2:
-         while (i<128/4) buffer[i] = v & 0xff, v += 33, ++i;
+         while (i<128/4) buffer[i] = (png_byte)(v & 0xff), v += 33, ++i;
          return;
 
       case 4:
-         while (i<128/2) buffer[i] = v & 0xff, v += 65, ++i;
+         while (i<128/2) buffer[i] = (png_byte)(v & 0xff), v += 65, ++i;
          return;
 
       case 8:
          /* 256 bytes total, 128 bytes in each row set as follows: */
-         while (i<128) buffer[i] = v & 0xff, ++v, ++i;
+         while (i<128) buffer[i] = (png_byte)(v & 0xff), ++v, ++i;
          return;
 
       case 16:
@@ -3187,7 +3187,12 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
           * GA case as well as the 16 bit G case.
           */
          while (i<128)
-            buffer[2*i] = (v>>8) & 0xff, buffer[2*i+1] = v & 0xff, ++v, ++i;
+         {
+            buffer[2*i] = (png_byte)((v>>8) & 0xff);
+            buffer[2*i+1] = (png_byte)(v & 0xff);
+            ++v;
+            ++i;
+         }
 
          return;
 
@@ -3196,9 +3201,9 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
          while (i<128)
          {
             /* Three bytes per pixel, r, g, b, make b by r^g */
-            buffer[3*i+0] = (v >> 8) & 0xff;
+            buffer[3*i+0] = (png_byte)((v >> 8) & 0xff);
-            buffer[3*i+1] = v & 0xff;
+            buffer[3*i+1] = (png_byte)(v & 0xff);
-            buffer[3*i+2] = ((v >> 8) ^ v) & 0xff;
+            buffer[3*i+2] = (png_byte)(((v >> 8) ^ v) & 0xff);
             ++v;
             ++i;
          }
@@ -3209,10 +3214,10 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
          /* 65535 pixels, r, g, b, a; just replicate */
          while (i<128)
          {
-            buffer[4*i+0] = (v >> 8) & 0xff;
+            buffer[4*i+0] = (png_byte)((v >> 8) & 0xff);
-            buffer[4*i+1] = v & 0xff;
+            buffer[4*i+1] = (png_byte)(v & 0xff);
-            buffer[4*i+2] = (v >> 8) & 0xff;
+            buffer[4*i+2] = (png_byte)((v >> 8) & 0xff);
-            buffer[4*i+3] = v & 0xff;
+            buffer[4*i+3] = (png_byte)(v & 0xff);
             ++v;
             ++i;
          }
@@ -3226,14 +3231,14 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
          while (i<128)
          {
             png_uint_32 t = v++;
-            buffer[6*i+0] = (t >> 8) & 0xff;
+            buffer[6*i+0] = (png_byte)((t >> 8) & 0xff);
-            buffer[6*i+1] = t & 0xff;
+            buffer[6*i+1] = (png_byte)(t & 0xff);
             t *= 257;
-            buffer[6*i+2] = (t >> 8) & 0xff;
+            buffer[6*i+2] = (png_byte)((t >> 8) & 0xff);
-            buffer[6*i+3] = t & 0xff;
+            buffer[6*i+3] = (png_byte)(t & 0xff);
             t *= 17;
-            buffer[6*i+4] = (t >> 8) & 0xff;
+            buffer[6*i+4] = (png_byte)((t >> 8) & 0xff);
-            buffer[6*i+5] = t & 0xff;
+            buffer[6*i+5] = (png_byte)(t & 0xff);
             ++i;
          }
 
@@ -3244,15 +3249,15 @@ transform_row(png_const_structp pp, png_byte buffer[TRANSFORM_ROWMAX],
          while (i<128)
          {
             png_uint_32 t = v++;
-            buffer[8*i+0] = (t >> 8) & 0xff;
+            buffer[8*i+0] = (png_byte)((t >> 8) & 0xff);
-            buffer[8*i+1] = t & 0xff;
+            buffer[8*i+1] = (png_byte)(t & 0xff);
-            buffer[8*i+4] = (t >> 8) & 0xff;
+            buffer[8*i+4] = (png_byte)((t >> 8) & 0xff);
-            buffer[8*i+5] = t & 0xff;
+            buffer[8*i+5] = (png_byte)(t & 0xff);
             t *= 257;
-            buffer[8*i+2] = (t >> 8) & 0xff;
+            buffer[8*i+2] = (png_byte)((t >> 8) & 0xff);
-            buffer[8*i+3] = t & 0xff;
+            buffer[8*i+3] = (png_byte)(t & 0xff);
-            buffer[8*i+6] = (t >> 8) & 0xff;
+            buffer[8*i+6] = (png_byte)((t >> 8) & 0xff);
-            buffer[8*i+7] = t & 0xff;
+            buffer[8*i+7] = (png_byte)(t & 0xff);
             ++i;
          }
          return;
@@ -4591,8 +4596,8 @@ standard_row_validate(standard_display *dp, png_const_structp pp,
             dp->bit_width)) != 0)
    {
       char msg[64];
-      sprintf(msg, "PNG image row[%d][%d] changed from %.2x to %.2x", y,
+      sprintf(msg, "PNG image row[%lu][%d] changed from %.2x to %.2x",
-         where-1, std[where-1],
+         (unsigned long)y, where-1, std[where-1],
          store_image_row(dp->ps, pp, iImage, y)[where-1]);
       png_error(pp, msg);
    }
@@ -4609,8 +4614,8 @@ standard_row_validate(standard_display *dp, png_const_structp pp,
          dp->bit_width)) != 0)
    {
       char msg[64];
-      sprintf(msg, "display  row[%d][%d] changed from %.2x to %.2x", y,
+      sprintf(msg, "display  row[%lu][%d] changed from %.2x to %.2x",
-         where-1, std[where-1],
+         (unsigned long)y, where-1, std[where-1],
          store_image_row(dp->ps, pp, iDisplay, y)[where-1]);
       png_error(pp, msg);
    }
@@ -8277,7 +8282,8 @@ gamma_image_validate(gamma_display *dp, png_const_structp pp,
          char msg[64];
 
          /* No transform is expected on the threshold tests. */
-         sprintf(msg, "gamma: below threshold row %d changed", y);
+         sprintf(msg, "gamma: below threshold row %lu changed",
+            (unsigned long)y);
 
          png_error(pp, msg);
       }
@@ -9425,7 +9431,7 @@ static void signal_handler(int signum)
 }
 
 /* main program */
-int main(int argc, PNG_CONST char **argv)
+int main(int argc, char **argv)
 {
    volatile int summary = 1;  /* Print the error summary at the end */
    volatile int memstats = 0; /* Print memory statistics at the end */

pngrtran.c

@@ -3508,8 +3508,9 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                      if ((png_uint_16)((*sp >> shift) & 0x01)
                         == png_ptr->trans_color.gray)
                      {
-                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
+                        unsigned int tmp = *sp & (0x7f7f >> (7 - shift));
-                        *sp |= (png_byte)(png_ptr->background.gray << shift);
+                        tmp |= png_ptr->background.gray << shift;
+                        *sp = (png_byte)(tmp & 0xff);
                      }
 
                      if (!shift)
@@ -3536,17 +3537,19 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                         if ((png_uint_16)((*sp >> shift) & 0x03)
                             == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         else
                         {
-                           png_byte p = (png_byte)((*sp >> shift) & 0x03);
+                           unsigned int p = (*sp >> shift) & 0x03;
-                           png_byte g = (png_byte)((gamma_table [p | (p << 2) |
+                           unsigned int g = (gamma_table [p | (p << 2) |
-                               (p << 4) | (p << 6)] >> 6) & 0x03);
+                               (p << 4) | (p << 6)] >> 6) & 0x03;
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(g << shift);
+                           tmp |= g << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         if (!shift)
@@ -3570,8 +3573,9 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                         if ((png_uint_16)((*sp >> shift) & 0x03)
                             == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0x3f3f >> (6 - shift));
-                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         if (!shift)
@@ -3599,17 +3603,19 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
                             == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         else
                         {
-                           png_byte p = (png_byte)((*sp >> shift) & 0x0f);
+                           unsigned int p = (*sp >> shift) & 0x0f;
-                           png_byte g = (png_byte)((gamma_table[p |
+                           unsigned int g = (gamma_table[p | (p << 4)] >> 4) &
-                               (p << 4)] >> 4) & 0x0f);
+                              0x0f;
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(g << shift);
+                           tmp |= g << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         if (!shift)
@@ -3633,8 +3639,9 @@ png_do_compose(png_row_infop row_info, png_bytep row, png_structrp png_ptr)
                         if ((png_uint_16)((*sp >> shift) & 0x0f)
                             == png_ptr->trans_color.gray)
                         {
-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           unsigned int tmp = *sp & (0xf0f >> (4 - shift));
-                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                           tmp |= png_ptr->background.gray << shift;
+                           *sp = (png_byte)(tmp & 0xff);
                         }
 
                         if (!shift)
@@ -4617,7 +4624,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
    {
       if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
       {
-         png_uint_16 gray = (png_uint_16)(trans_color ? trans_color->gray : 0);
+         unsigned int gray = trans_color ? trans_color->gray : 0;
 
          if (row_info->bit_depth < 8)
          {
@@ -4625,7 +4632,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
             {
                case 1:
                {
-                  gray = (png_uint_16)((gray & 0x01) * 0xff);
+                  gray = (gray & 0x01) * 0xff;
                   sp = row + (png_size_t)((row_width - 1) >> 3);
                   dp = row + (png_size_t)row_width - 1;
                   shift = 7 - (int)((row_width + 7) & 0x07);
@@ -4653,7 +4660,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 
                case 2:
                {
-                  gray = (png_uint_16)((gray & 0x03) * 0x55);
+                  gray = (gray & 0x03) * 0x55;
                   sp = row + (png_size_t)((row_width - 1) >> 2);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
@@ -4678,7 +4685,7 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 
                case 4:
                {
-                  gray = (png_uint_16)((gray & 0x0f) * 0x11);
+                  gray = (gray & 0x0f) * 0x11;
                   sp = row + (png_size_t)((row_width - 1) >> 1);
                   dp = row + (png_size_t)row_width - 1;
                   shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
@@ -4731,8 +4738,8 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 
             else if (row_info->bit_depth == 16)
             {
-               png_byte gray_high = (png_byte)((gray >> 8) & 0xff);
+               unsigned int gray_high = (gray >> 8) & 0xff;
-               png_byte gray_low = (png_byte)(gray & 0xff);
+               unsigned int gray_low = gray & 0xff;
                sp = row + row_info->rowbytes - 1;
                dp = row + (row_info->rowbytes << 1) - 1;
                for (i = 0; i < row_width; i++)

pngrutil.c

@@ -3315,8 +3315,9 @@ png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
                v = (png_byte)((*sp >> sshift) & 0x01);
                for (j = 0; j < jstop; j++)
                {
-                  *dp &= (png_byte)((0x7f7f >> (7 - dshift)) & 0xff);
+                  unsigned int tmp = *dp & (0x7f7f >> (7 - dshift));
-                  *dp |= (png_byte)(v << dshift);
+                  tmp |= v << dshift;
+                  *dp = (png_byte)(tmp & 0xff);
 
                   if (dshift == s_end)
                   {
@@ -3377,8 +3378,9 @@ png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
                v = (png_byte)((*sp >> sshift) & 0x03);
                for (j = 0; j < jstop; j++)
                {
-                  *dp &= (png_byte)((0x3f3f >> (6 - dshift)) & 0xff);
+                  unsigned int tmp = *dp & (0x3f3f >> (6 - dshift));
-                  *dp |= (png_byte)(v << dshift);
+                  tmp |= v << dshift;
+                  *dp = (png_byte)(tmp & 0xff);
 
                   if (dshift == s_end)
                   {
@@ -3438,8 +3440,9 @@ png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
 
                for (j = 0; j < jstop; j++)
                {
-                  *dp &= (png_byte)((0xf0f >> (4 - dshift)) & 0xff);
+                  unsigned int tmp = *dp & (0xf0f >> (4 - dshift));
-                  *dp |= (png_byte)(v << dshift);
+                  tmp |= v << dshift;
+                  *dp = (png_byte)(tmp & 0xff);
 
                   if (dshift == s_end)
                   {

pngtest.c

@@ -89,8 +89,6 @@ static char tIME_string[PNG_tIME_STRING_LENGTH] = "tIME chunk is not present";
 static int verbose = 0;
 static int strict = 0;
 
-int test_one_file PNGARG((PNG_CONST char *inname, PNG_CONST char *outname));
-
 #ifdef __TURBOC__
 #include <mem.h>
 #endif
@@ -109,9 +107,7 @@ static int status_pass = 1;
 static int status_dots_requested = 0;
 static int status_dots = 1;
 
-void PNGCBAPI
+static void PNGCBAPI
-read_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass);
-void PNGCBAPI
 read_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass)
 {
    if (png_ptr == NULL || row_number > PNG_UINT_31_MAX)
@@ -135,9 +131,7 @@ read_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass)
    fprintf(stdout, "r");
 }
 
-void PNGCBAPI
+static void PNGCBAPI
-write_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass);
-void PNGCBAPI
 write_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass)
 {
    if (png_ptr == NULL || row_number > PNG_UINT_31_MAX || pass > 7)
@@ -153,9 +147,7 @@ write_row_callback(png_structp png_ptr, png_uint_32 row_number, int pass)
  * 5 in case illegal filter values are present.)
  */
 static png_uint_32 filters_used[256];
-void PNGCBAPI
+static void PNGCBAPI
-count_filters(png_structp png_ptr, png_row_infop row_info, png_bytep data);
-void PNGCBAPI
 count_filters(png_structp png_ptr, png_row_infop row_info, png_bytep data)
 {
    if (png_ptr != NULL && row_info != NULL)
@@ -170,9 +162,7 @@ count_filters(png_structp png_ptr, png_row_infop row_info, png_bytep data)
 
 static png_uint_32 zero_samples;
 
-void PNGCBAPI
+static void PNGCBAPI
-count_zero_samples(png_structp png_ptr, png_row_infop row_info, png_bytep data);
-void PNGCBAPI
 count_zero_samples(png_structp png_ptr, png_row_infop row_info, png_bytep data)
 {
    png_bytep dp = data;
@@ -636,7 +626,7 @@ static int PNGCBAPI read_user_chunk_callback(png_struct *png_ptr,
 /* END of code to demonstrate user chunk support */
 
 /* Test one file */
-int
+static int
 test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 {
    static png_FILE_p fpin;

pngtrans.c

@@ -648,7 +648,7 @@ png_get_user_transform_ptr(png_const_structrp png_ptr)
    if (png_ptr == NULL)
       return (NULL);
 
-   return ((png_voidp)png_ptr->user_transform_ptr);
+   return png_ptr->user_transform_ptr;
 }
 #endif
 

pngwtran.c

@@ -287,7 +287,7 @@ png_do_shift(png_row_infop row_info, png_bytep row,
       {
          png_bytep bp = row;
          png_size_t i;
-         png_byte mask;
+         unsigned int mask;
          png_size_t row_bytes = row_info->rowbytes;
 
          if (bit_depth->gray == 1 && row_info->bit_depth == 2)
@@ -301,20 +301,22 @@ png_do_shift(png_row_infop row_info, png_bytep row,
 
          for (i = 0; i < row_bytes; i++, bp++)
          {
-            png_uint_16 v;
             int j;
+            unsigned int v, out;
 
             v = *bp;
-            *bp = 0;
+            out = 0;
 
             for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
             {
                if (j > 0)
-                  *bp |= (png_byte)((v << j) & 0xff);
+                  out |= v << j;
 
                else
-                  *bp |= (png_byte)((v >> (-j)) & mask);
+                  out |= (v >> (-j)) & mask;
             }
+
+            *bp = (png_byte)(out & 0xff);
          }
       }
 
@@ -327,21 +329,23 @@ png_do_shift(png_row_infop row_info, png_bytep row,
          for (i = 0; i < istop; i++, bp++)
          {
 
-            png_uint_16 v;
+            const unsigned int c = i%channels;
             int j;
-            int c = (int)(i%channels);
+            unsigned int v, out;
 
             v = *bp;
-            *bp = 0;
+            out = 0;
 
             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
             {
                if (j > 0)
-                  *bp |= (png_byte)((v << j) & 0xff);
+                  out |= v << j;
 
                else
-                  *bp |= (png_byte)((v >> (-j)) & 0xff);
+                  out |= v >> (-j);
             }
+
+            *bp = (png_byte)(out & 0xff);
          }
       }
 
@@ -353,22 +357,22 @@ png_do_shift(png_row_infop row_info, png_bytep row,
 
          for (bp = row, i = 0; i < istop; i++)
          {
-            int c = (int)(i%channels);
+            const unsigned int c = i%channels;
-            png_uint_16 value, v;
             int j;
+            unsigned int value, v;
 
-            v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
+            v = png_get_uint_16(bp);
             value = 0;
 
             for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
             {
                if (j > 0)
-                  value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
+                  value |= v << j;
 
                else
-                  value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
+                  value |= v >> (-j);
             }
-            *bp++ = (png_byte)(value >> 8);
+            *bp++ = (png_byte)((value >> 8) & 0xff);
             *bp++ = (png_byte)(value & 0xff);
          }
       }