Imported from pngcrush-1.6.5.tar

pngwutil.c

@@ -1,9 +1,9 @@
 
 /* pngwutil.c - utilities to write a PNG file
  *
- * Last changed in libpng 1.2.11 June 4, 2006
+ * Last changed in libpng 1.2.27 [April 29, 2008]
  * For conditions of distribution and use, see copyright notice in png.h
- * Copyright (c) 1998-2006 Glenn Randers-Pehrson
+ * Copyright (c) 1998-2008 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  */
@@ -62,6 +62,7 @@ void PNGAPI
 png_write_chunk(png_structp png_ptr, png_bytep chunk_name,
    png_bytep data, png_size_t length)
 {
+   if(png_ptr == NULL) return;
    png_write_chunk_start(png_ptr, chunk_name, (png_uint_32)length);
    png_write_chunk_data(png_ptr, data, length);
    png_write_chunk_end(png_ptr);
@@ -77,6 +78,7 @@ png_write_chunk_start(png_structp png_ptr, png_bytep chunk_name,
 {
    png_byte buf[4];
    png_debug2(0, "Writing %s chunk (%lu bytes)\n", chunk_name, length);
+   if(png_ptr == NULL) return;
 
    /* write the length */
    png_save_uint_32(buf, length);
@@ -98,6 +100,7 @@ void PNGAPI
 png_write_chunk_data(png_structp png_ptr, png_bytep data, png_size_t length)
 {
    /* write the data, and run the CRC over it */
+   if(png_ptr == NULL) return;
    if (data != NULL && length > 0)
    {
       png_calculate_crc(png_ptr, data, length);
@@ -111,6 +114,8 @@ png_write_chunk_end(png_structp png_ptr)
 {
    png_byte buf[4];
 
+   if(png_ptr == NULL) return;
+
    /* write the crc */
    png_save_uint_32(buf, png_ptr->crc);
 
@@ -177,7 +182,7 @@ png_text_compress(png_structp png_ptr,
    {
 #if !defined(PNG_NO_STDIO) && !defined(_WIN32_WCE)
       char msg[50];
-      sprintf(msg, "Unknown compression type %d", compression);
+      png_snprintf(msg, 50, "Unknown compression type %d", compression);
       png_warning(png_ptr, msg);
 #else
       png_warning(png_ptr, "Unknown compression type");
@@ -375,6 +380,8 @@ png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
 #ifdef PNG_USE_LOCAL_ARRAYS
    PNG_IHDR;
 #endif
+   int ret;
+
    png_byte buf[13]; /* buffer to store the IHDR info */
 
    png_debug(1, "in png_write_IHDR\n");
@@ -489,7 +496,7 @@ png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
    buf[12] = (png_byte)interlace_type;
 
    /* write the chunk */
-   png_write_chunk(png_ptr, (png_bytep)png_IHDR, buf, (png_size_t)13);
+   png_write_chunk(png_ptr, png_IHDR, buf, (png_size_t)13);
 
    /* initialize zlib with PNG info */
    png_ptr->zstream.zalloc = png_zalloc;
@@ -518,9 +525,19 @@ png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
       png_ptr->zlib_window_bits = 15;
    if (!(png_ptr->flags & PNG_FLAG_ZLIB_CUSTOM_METHOD))
       png_ptr->zlib_method = 8;
-   deflateInit2(&png_ptr->zstream, png_ptr->zlib_level,
-      png_ptr->zlib_method, png_ptr->zlib_window_bits,
-      png_ptr->zlib_mem_level, png_ptr->zlib_strategy);
+   ret = deflateInit2(&png_ptr->zstream, png_ptr->zlib_level,
+         png_ptr->zlib_method, png_ptr->zlib_window_bits,
+         png_ptr->zlib_mem_level, png_ptr->zlib_strategy);
+   if (ret != Z_OK)
+   {
+      if (ret == Z_VERSION_ERROR) png_error(png_ptr,
+          "zlib failed to initialize compressor -- version error");
+      if (ret == Z_STREAM_ERROR) png_error(png_ptr,
+           "zlib failed to initialize compressor -- stream error");
+      if (ret == Z_MEM_ERROR) png_error(png_ptr,
+           "zlib failed to initialize compressor -- mem error");
+      png_error(png_ptr, "zlib failed to initialize compressor");
+   }
    png_ptr->zstream.next_out = png_ptr->zbuf;
    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
    /* libpng is not interested in zstream.data_type */
@@ -572,7 +589,7 @@ png_write_PLTE(png_structp png_ptr, png_colorp palette, png_uint_32 num_pal)
    png_ptr->num_palette = (png_uint_16)num_pal;
    png_debug1(3, "num_palette = %d\n", png_ptr->num_palette);
 
-   png_write_chunk_start(png_ptr, (png_bytep)png_PLTE, num_pal * 3);
+   png_write_chunk_start(png_ptr, png_PLTE, num_pal * 3);
 #ifndef PNG_NO_POINTER_INDEXING
    for (i = 0, pal_ptr = palette; i < num_pal; i++, pal_ptr++)
    {
@@ -644,7 +661,7 @@ png_write_IDAT(png_structp png_ptr, png_bytep data, png_size_t length)
             "Invalid zlib compression method or flags in IDAT");
    }
 
-   png_write_chunk(png_ptr, (png_bytep)png_IDAT, data, length);
+   png_write_chunk(png_ptr, png_IDAT, data, length);
    png_ptr->mode |= PNG_HAVE_IDAT;
 }
 
@@ -656,7 +673,7 @@ png_write_IEND(png_structp png_ptr)
    PNG_IEND;
 #endif
    png_debug(1, "in png_write_IEND\n");
-   png_write_chunk(png_ptr, (png_bytep)png_IEND, png_bytep_NULL,
+   png_write_chunk(png_ptr, png_IEND, png_bytep_NULL,
      (png_size_t)0);
    png_ptr->mode |= PNG_HAVE_IEND;
 }
@@ -677,7 +694,7 @@ png_write_gAMA(png_structp png_ptr, double file_gamma)
    /* file_gamma is saved in 1/100,000ths */
    igamma = (png_uint_32)(file_gamma * 100000.0 + 0.5);
    png_save_uint_32(buf, igamma);
-   png_write_chunk(png_ptr, (png_bytep)png_gAMA, buf, (png_size_t)4);
+   png_write_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
 }
 #endif
 #ifdef PNG_FIXED_POINT_SUPPORTED
@@ -692,7 +709,7 @@ png_write_gAMA_fixed(png_structp png_ptr, png_fixed_point file_gamma)
    png_debug(1, "in png_write_gAMA\n");
    /* file_gamma is saved in 1/100,000ths */
    png_save_uint_32(buf, (png_uint_32)file_gamma);
-   png_write_chunk(png_ptr, (png_bytep)png_gAMA, buf, (png_size_t)4);
+   png_write_chunk(png_ptr, png_gAMA, buf, (png_size_t)4);
 }
 #endif
 #endif
@@ -712,7 +729,7 @@ png_write_sRGB(png_structp png_ptr, int srgb_intent)
          png_warning(png_ptr,
             "Invalid sRGB rendering intent specified");
    buf[0]=(png_byte)srgb_intent;
-   png_write_chunk(png_ptr, (png_bytep)png_sRGB, buf, (png_size_t)1);
+   png_write_chunk(png_ptr, png_sRGB, buf, (png_size_t)1);
 }
 #endif
 
@@ -728,6 +745,7 @@ png_write_iCCP(png_structp png_ptr, png_charp name, int compression_type,
    png_size_t name_len;
    png_charp new_name;
    compression_state comp;
+   int embedded_profile_len = 0;
 
    png_debug(1, "in png_write_iCCP\n");
 
@@ -750,12 +768,33 @@ png_write_iCCP(png_structp png_ptr, png_charp name, int compression_type,
    if (profile == NULL)
       profile_len = 0;
 
+   if (profile_len > 3)
+      embedded_profile_len =
+          ((*( (png_bytep)profile  ))<<24) |
+          ((*( (png_bytep)profile+1))<<16) |
+          ((*( (png_bytep)profile+2))<< 8) |
+          ((*( (png_bytep)profile+3))    );
+
+   if (profile_len < embedded_profile_len)
+     {
+        png_warning(png_ptr,
+          "Embedded profile length too large in iCCP chunk");
+        return;
+     }
+
+   if (profile_len > embedded_profile_len)
+     {
+        png_warning(png_ptr,
+          "Truncating profile to actual length in iCCP chunk");
+        profile_len = embedded_profile_len;
+     }
+
    if (profile_len)
        profile_len = png_text_compress(png_ptr, profile, (png_size_t)profile_len,
           PNG_COMPRESSION_TYPE_BASE, &comp);
 
    /* make sure we include the NULL after the name and the compression type */
-   png_write_chunk_start(png_ptr, (png_bytep)png_iCCP,
+   png_write_chunk_start(png_ptr, png_iCCP,
           (png_uint_32)name_len+profile_len+2);
    new_name[name_len+1]=0x00;
    png_write_chunk_data(png_ptr, (png_bytep)new_name, name_len + 2);
@@ -795,7 +834,7 @@ png_write_sPLT(png_structp png_ptr, png_sPLT_tp spalette)
    }
 
    /* make sure we include the NULL after the name */
-   png_write_chunk_start(png_ptr, (png_bytep)png_sPLT,
+   png_write_chunk_start(png_ptr, png_sPLT,
           (png_uint_32)(name_len + 2 + palette_size));
    png_write_chunk_data(png_ptr, (png_bytep)new_name, name_len + 1);
    png_write_chunk_data(png_ptr, (png_bytep)&spalette->depth, 1);
@@ -903,7 +942,7 @@ png_write_sBIT(png_structp png_ptr, png_color_8p sbit, int color_type)
       buf[size++] = sbit->alpha;
    }
 
-   png_write_chunk(png_ptr, (png_bytep)png_sBIT, buf, size);
+   png_write_chunk(png_ptr, png_sBIT, buf, size);
 }
 #endif
 
@@ -967,7 +1006,7 @@ png_write_cHRM(png_structp png_ptr, double white_x, double white_y,
    itemp = (png_uint_32)(blue_y * 100000.0 + 0.5);
    png_save_uint_32(buf + 28, itemp);
 
-   png_write_chunk(png_ptr, (png_bytep)png_cHRM, buf, (png_size_t)32);
+   png_write_chunk(png_ptr, png_cHRM, buf, (png_size_t)32);
 }
 #endif
 #ifdef PNG_FIXED_POINT_SUPPORTED
@@ -1019,7 +1058,7 @@ png_write_cHRM_fixed(png_structp png_ptr, png_fixed_point white_x,
    png_save_uint_32(buf + 24, (png_uint_32)blue_x);
    png_save_uint_32(buf + 28, (png_uint_32)blue_y);
 
-   png_write_chunk(png_ptr, (png_bytep)png_cHRM, buf, (png_size_t)32);
+   png_write_chunk(png_ptr, png_cHRM, buf, (png_size_t)32);
 }
 #endif
 #endif
@@ -1044,7 +1083,7 @@ png_write_tRNS(png_structp png_ptr, png_bytep trans, png_color_16p tran,
          return;
       }
       /* write the chunk out as it is */
-      png_write_chunk(png_ptr, (png_bytep)png_tRNS, trans, (png_size_t)num_trans);
+      png_write_chunk(png_ptr, png_tRNS, trans, (png_size_t)num_trans);
    }
    else if (color_type == PNG_COLOR_TYPE_GRAY)
    {
@@ -1056,7 +1095,7 @@ png_write_tRNS(png_structp png_ptr, png_bytep trans, png_color_16p tran,
          return;
       }
       png_save_uint_16(buf, tran->gray);
-      png_write_chunk(png_ptr, (png_bytep)png_tRNS, buf, (png_size_t)2);
+      png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)2);
    }
    else if (color_type == PNG_COLOR_TYPE_RGB)
    {
@@ -1070,7 +1109,7 @@ png_write_tRNS(png_structp png_ptr, png_bytep trans, png_color_16p tran,
               "Ignoring attempt to write 16-bit tRNS chunk when bit_depth is 8");
             return;
          }
-      png_write_chunk(png_ptr, (png_bytep)png_tRNS, buf, (png_size_t)6);
+      png_write_chunk(png_ptr, png_tRNS, buf, (png_size_t)6);
    }
    else
    {
@@ -1103,7 +1142,7 @@ png_write_bKGD(png_structp png_ptr, png_color_16p back, int color_type)
          return;
       }
       buf[0] = back->index;
-      png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)1);
+      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)1);
    }
    else if (color_type & PNG_COLOR_MASK_COLOR)
    {
@@ -1116,7 +1155,7 @@ png_write_bKGD(png_structp png_ptr, png_color_16p back, int color_type)
               "Ignoring attempt to write 16-bit bKGD chunk when bit_depth is 8");
             return;
          }
-      png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)6);
+      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)6);
    }
    else
    {
@@ -1127,7 +1166,7 @@ png_write_bKGD(png_structp png_ptr, png_color_16p back, int color_type)
          return;
       }
       png_save_uint_16(buf, back->gray);
-      png_write_chunk(png_ptr, (png_bytep)png_bKGD, buf, (png_size_t)2);
+      png_write_chunk(png_ptr, png_bKGD, buf, (png_size_t)2);
    }
 }
 #endif
@@ -1152,7 +1191,7 @@ png_write_hIST(png_structp png_ptr, png_uint_16p hist, int num_hist)
       return;
    }
 
-   png_write_chunk_start(png_ptr, (png_bytep)png_hIST, (png_uint_32)(num_hist * 2));
+   png_write_chunk_start(png_ptr, png_hIST, (png_uint_32)(num_hist * 2));
    for (i = 0; i < num_hist; i++)
    {
       png_save_uint_16(buf, hist[i]);
@@ -1203,12 +1242,14 @@ png_check_keyword(png_structp png_ptr, png_charp key, png_charpp new_key)
    /* Replace non-printing characters with a blank and print a warning */
    for (kp = key, dp = *new_key; *kp != '\0'; kp++, dp++)
    {
-      if (*kp < 0x20 || (*kp > 0x7E && (png_byte)*kp < 0xA1))
+      if ((png_byte)*kp < 0x20 ||
+         ((png_byte)*kp > 0x7E && (png_byte)*kp < 0xA1))
       {
 #if !defined(PNG_NO_STDIO) && !defined(_WIN32_WCE)
          char msg[40];
 
-         sprintf(msg, "invalid keyword character 0x%02X", *kp);
+         png_snprintf(msg, 40,
+           "invalid keyword character 0x%02X", (png_byte)*kp);
          png_warning(png_ptr, msg);
 #else
          png_warning(png_ptr, "invalid character in keyword");
@@ -1316,7 +1357,7 @@ png_write_tEXt(png_structp png_ptr, png_charp key, png_charp text,
       text_len = png_strlen(text);
 
    /* make sure we include the 0 after the key */
-   png_write_chunk_start(png_ptr, (png_bytep)png_tEXt, (png_uint_32)key_len+text_len+1);
+   png_write_chunk_start(png_ptr, png_tEXt, (png_uint_32)key_len+text_len+1);
    /*
     * We leave it to the application to meet PNG-1.0 requirements on the
     * contents of the text.  PNG-1.0 through PNG-1.2 discourage the use of
@@ -1369,17 +1410,17 @@ png_write_zTXt(png_structp png_ptr, png_charp key, png_charp text,
 
    text_len = png_strlen(text);
 
-   png_free(png_ptr, new_key);
-
    /* compute the compressed data; do it now for the length */
    text_len = png_text_compress(png_ptr, text, text_len, compression,
        &comp);
 
    /* write start of chunk */
-   png_write_chunk_start(png_ptr, (png_bytep)png_zTXt, (png_uint_32)
+   png_write_chunk_start(png_ptr, png_zTXt, (png_uint_32)
       (key_len+text_len+2));
    /* write key */
-   png_write_chunk_data(png_ptr, (png_bytep)key, key_len + 1);
+   png_write_chunk_data(png_ptr, (png_bytep)new_key, key_len + 1);
+   png_free(png_ptr, new_key);
+
    buf[0] = (png_byte)compression;
    /* write compression */
    png_write_chunk_data(png_ptr, (png_bytep)buf, (png_size_t)1);
@@ -1442,7 +1483,7 @@ png_write_iTXt(png_structp png_ptr, int compression, png_charp key,
    /* make sure we include the compression flag, the compression byte,
     * and the NULs after the key, lang, and lang_key parts */
 
-   png_write_chunk_start(png_ptr, (png_bytep)png_iTXt,
+   png_write_chunk_start(png_ptr, png_iTXt,
           (png_uint_32)(
         5 /* comp byte, comp flag, terminators for key, lang and lang_key */
         + key_len
@@ -1475,8 +1516,7 @@ png_write_iTXt(png_structp png_ptr, int compression, png_charp key,
 
    png_write_chunk_end(png_ptr);
    png_free(png_ptr, new_key);
-   if (new_lang)
-     png_free(png_ptr, new_lang);
+   png_free(png_ptr, new_lang);
 }
 #endif
 
@@ -1499,10 +1539,9 @@ png_write_oFFs(png_structp png_ptr, png_int_32 x_offset, png_int_32 y_offset,
    png_save_int_32(buf + 4, y_offset);
    buf[8] = (png_byte)unit_type;
 
-   png_write_chunk(png_ptr, (png_bytep)png_oFFs, buf, (png_size_t)9);
+   png_write_chunk(png_ptr, png_oFFs, buf, (png_size_t)9);
 }
 #endif
-
 #if defined(PNG_WRITE_pCAL_SUPPORTED)
 /* write the pCAL chunk (described in the PNG extensions document) */
 void /* PRIVATE */
@@ -1541,7 +1580,7 @@ png_write_pCAL(png_structp png_ptr, png_charp purpose, png_int_32 X0,
    }
 
    png_debug1(3, "pCAL total length = %d\n", (int)total_len);
-   png_write_chunk_start(png_ptr, (png_bytep)png_pCAL, (png_uint_32)total_len);
+   png_write_chunk_start(png_ptr, png_pCAL, (png_uint_32)total_len);
    png_write_chunk_data(png_ptr, (png_bytep)new_purpose, purpose_len);
    png_save_int_32(buf, X0);
    png_save_int_32(buf + 4, X1);
@@ -1594,14 +1633,14 @@ png_write_sCAL(png_structp png_ptr, int unit, double width, double height)
       total_len += wc_len;
    }
 #else
-   sprintf(buf + 1, "%12.12e", width);
+   png_snprintf(buf + 1, 63, "%12.12e", width);
    total_len = 1 + png_strlen(buf + 1) + 1;
-   sprintf(buf + total_len, "%12.12e", height);
+   png_snprintf(buf + total_len, 64-total_len, "%12.12e", height);
    total_len += png_strlen(buf + total_len);
 #endif
 
    png_debug1(3, "sCAL total length = %u\n", (unsigned int)total_len);
-   png_write_chunk(png_ptr, (png_bytep)png_sCAL, (png_bytep)buf, total_len);
+   png_write_chunk(png_ptr, png_sCAL, (png_bytep)buf, total_len);
 }
 #else
 #ifdef PNG_FIXED_POINT_SUPPORTED
@@ -1631,7 +1670,7 @@ png_write_sCAL_s(png_structp png_ptr, int unit, png_charp width,
    png_memcpy(buf + wlen + 2, height, hlen);  /* do NOT append the '\0' here */
 
    png_debug1(3, "sCAL total length = %u\n", (unsigned int)total_len);
-   png_write_chunk(png_ptr, (png_bytep)png_sCAL, buf, total_len);
+   png_write_chunk(png_ptr, png_sCAL, buf, total_len);
 }
 #endif
 #endif
@@ -1657,7 +1696,7 @@ png_write_pHYs(png_structp png_ptr, png_uint_32 x_pixels_per_unit,
    png_save_uint_32(buf + 4, y_pixels_per_unit);
    buf[8] = (png_byte)unit_type;
 
-   png_write_chunk(png_ptr, (png_bytep)png_pHYs, buf, (png_size_t)9);
+   png_write_chunk(png_ptr, png_pHYs, buf, (png_size_t)9);
 }
 #endif
 
@@ -1689,7 +1728,7 @@ png_write_tIME(png_structp png_ptr, png_timep mod_time)
    buf[5] = mod_time->minute;
    buf[6] = mod_time->second;
 
-   png_write_chunk(png_ptr, (png_bytep)png_tIME, buf, (png_size_t)7);
+   png_write_chunk(png_ptr, png_tIME, buf, (png_size_t)7);
 }
 #endif
 
@@ -1697,6 +1736,7 @@ png_write_tIME(png_structp png_ptr, png_timep mod_time)
 void /* PRIVATE */
 png_write_start_row(png_structp png_ptr)
 {
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
 #ifdef PNG_USE_LOCAL_ARRAYS
    /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
@@ -1711,6 +1751,7 @@ png_write_start_row(png_structp png_ptr)
 
    /* offset to next interlace block in the y direction */
    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+#endif
 #endif
 
    png_size_t buf_size;
@@ -1723,6 +1764,7 @@ png_write_start_row(png_structp png_ptr)
    png_ptr->row_buf = (png_bytep)png_malloc(png_ptr, (png_uint_32)buf_size);
    png_ptr->row_buf[0] = PNG_FILTER_VALUE_NONE;
 
+#ifndef PNG_NO_WRITE_FILTERING
    /* set up filtering buffer, if using this filter */
    if (png_ptr->do_filter & PNG_FILTER_SUB)
    {
@@ -1740,7 +1782,7 @@ png_write_start_row(png_structp png_ptr)
 
       if (png_ptr->do_filter & PNG_FILTER_UP)
       {
-         png_ptr->up_row = (png_bytep )png_malloc(png_ptr,
+         png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
             (png_ptr->rowbytes + 1));
          png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
       }
@@ -1754,10 +1796,11 @@ png_write_start_row(png_structp png_ptr)
 
       if (png_ptr->do_filter & PNG_FILTER_PAETH)
       {
-         png_ptr->paeth_row = (png_bytep )png_malloc(png_ptr,
+         png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
             (png_ptr->rowbytes + 1));
          png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
       }
+#endif /* PNG_NO_WRITE_FILTERING */
    }
 
 #ifdef PNG_WRITE_INTERLACING_SUPPORTED
@@ -1791,6 +1834,7 @@ png_write_start_row(png_structp png_ptr)
 void /* PRIVATE */
 png_write_finish_row(png_structp png_ptr)
 {
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
 #ifdef PNG_USE_LOCAL_ARRAYS
    /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */
 
@@ -1805,6 +1849,7 @@ png_write_finish_row(png_structp png_ptr)
 
    /* offset to next interlace block in the y direction */
    int png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+#endif
 #endif
 
    int ret;
@@ -2079,7 +2124,9 @@ png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
 void /* PRIVATE */
 png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
 {
-   png_bytep prev_row, best_row, row_buf;
+   png_bytep best_row;
+#ifndef PNG_NO_WRITE_FILTER
+   png_bytep prev_row, row_buf;
    png_uint_32 mins, bpp;
    png_byte filter_to_do = png_ptr->do_filter;
    png_uint_32 row_bytes = row_info->rowbytes;
@@ -2092,7 +2139,10 @@ png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
    bpp = (row_info->pixel_depth + 7) >> 3;
 
    prev_row = png_ptr->prev_row;
-   best_row = row_buf = png_ptr->row_buf;
+#endif
+   best_row = png_ptr->row_buf;
+#ifndef PNG_NO_WRITE_FILTER
+   row_buf = best_row;
    mins = PNG_MAXSUM;
 
    /* The prediction method we use is to find which method provides the
@@ -2667,11 +2717,12 @@ png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
          best_row = png_ptr->paeth_row;
       }
    }
-
+#endif /* PNG_NO_WRITE_FILTER */
    /* Do the actual writing of the filtered row data from the chosen filter. */
 
    png_write_filtered_row(png_ptr, best_row);
 
+#ifndef PNG_NO_WRITE_FILTER
 #if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
    /* Save the type of filter we picked this time for future calculations */
    if (png_ptr->num_prev_filters > 0)
@@ -2684,6 +2735,7 @@ png_write_find_filter(png_structp png_ptr, png_row_infop row_info)
       png_ptr->prev_filters[j] = best_row[0];
    }
 #endif
+#endif /* PNG_NO_WRITE_FILTER */
 }