]> granicus.if.org Git - imagemagick/blobdiff - coders/jpeg.c
Check for sampling-factor option only if sampling-factor image property is NULL.
[imagemagick] / coders / jpeg.c
index b13ec4bef8880dedbfe0e5e83bcf8ea57c1caa44..2ff4b6578a8d7d1c8fe2b8532ec0dd834ae3d963 100644 (file)
@@ -17,7 +17,7 @@
 %                                 July 1992                                   %
 %                                                                             %
 %                                                                             %
-%  Copyright 1999-2011 ImageMagick Studio LLC, a non-profit organization      %
+%  Copyright 1999-2012 ImageMagick Studio LLC, a non-profit organization      %
 %  dedicated to making software imaging solutions freely available.           %
 %                                                                             %
 %  You may not use this file except in compliance with the License.  You may  %
 #include "MagickCore/static.h"
 #include "MagickCore/string_.h"
 #include "MagickCore/string-private.h"
+#include "MagickCore/token.h"
 #include "MagickCore/utility.h"
+#include "MagickCore/xml-tree.h"
+#include "MagickCore/xml-tree-private.h"
 #include <setjmp.h>
 #if defined(MAGICKCORE_JPEG_DELEGATE)
 #define JPEG_INTERNAL_OPTIONS
 #if defined(__MINGW32__)
 # define XMD_H 1  /* Avoid conflicting typedef for INT32 */
-typedef unsigned char boolean;
-#define HAVE_BOOLEAN
 #endif
 #undef HAVE_STDLIB_H
 #include "jpeglib.h"
@@ -98,7 +99,7 @@ typedef unsigned char boolean;
 #define ICC_PROFILE  "ICC_PROFILE"
 #define IPTC_MARKER  (JPEG_APP0+13)
 #define XML_MARKER  (JPEG_APP0+1)
-#define MaxBufferExtent  8192
+#define MaxBufferExtent  16384
 \f
 /*
   Typedef declarations.
@@ -146,6 +147,23 @@ typedef struct _SourceManager
     start_of_blob;
 } SourceManager;
 #endif
+
+typedef struct _QuantizationTable
+{
+  char
+    *slot,
+    *description;
+
+  size_t
+    width,
+    height;
+
+  double
+    divisor;
+
+  unsigned int
+    *levels;
+} QuantizationTable;
 \f
 /*
   Forward declarations.
@@ -228,7 +246,7 @@ static boolean FillInputBuffer(j_decompress_ptr cinfo)
     MaxBufferExtent,source->buffer);
   if (source->manager.bytes_in_buffer == 0)
     {
-      if (source->start_of_blob != 0)
+      if (source->start_of_blob != FALSE)
         ERREXIT(cinfo,JERR_INPUT_EMPTY);
       WARNMS(cinfo,JWRN_JPEG_EOF);
       source->buffer[0]=(JOCTET) 0xff;
@@ -310,6 +328,8 @@ static void JPEGErrorHandler(j_common_ptr jpeg_info)
 
 static MagickBooleanType JPEGWarningHandler(j_common_ptr jpeg_info,int level)
 {
+#define JPEGExcessiveWarnings  1000
+
   char
     message[JMSG_LENGTH_MAX];
 
@@ -332,11 +352,10 @@ static MagickBooleanType JPEGWarningHandler(j_common_ptr jpeg_info,int level)
         Process warning message.
       */
       (jpeg_info->err->format_message)(jpeg_info,message);
-      if ((jpeg_info->err->num_warnings == 0) ||
-          (jpeg_info->err->trace_level >= 3))
-        ThrowBinaryException(CorruptImageWarning,(char *) message,
-          image->filename);
-      jpeg_info->err->num_warnings++;
+      if (jpeg_info->err->num_warnings++ > JPEGExcessiveWarnings)
+        JPEGErrorHandler(jpeg_info);
+      ThrowBinaryException(CorruptImageWarning,(char *) message,
+        image->filename);
     }
   else
     if ((image->debug != MagickFalse) &&
@@ -674,7 +693,7 @@ static boolean ReadProfile(j_decompress_ptr jpeg_info)
   previous_profile=GetImageProfile(image,name);
   if (previous_profile != (const StringInfo *) NULL)
     {
-      ssize_t
+      size_t
         length;
 
       length=GetStringInfoLength(profile);
@@ -1044,14 +1063,6 @@ static Image *ReadJPEGImage(const ImageInfo *image_info,
       (image_info->colorspace == Rec601YCbCrColorspace) ||
       (image_info->colorspace == Rec709YCbCrColorspace))
     jpeg_info.out_color_space=JCS_YCbCr;
-  if (IsITUFaxImage(image) != MagickFalse)
-    {
-      image->colorspace=LabColorspace;
-      jpeg_info.out_color_space=JCS_YCbCr;
-    }
-  else
-    if (jpeg_info.out_color_space == JCS_CMYK)
-      image->colorspace=CMYKColorspace;
   /*
     Set image resolution.
   */
@@ -1127,17 +1138,15 @@ static Image *ReadJPEGImage(const ImageInfo *image_info,
   option=GetImageOption(image_info,"jpeg:colors");
   if (option != (const char *) NULL)
     {
-      /* Let the JPEG library quantize the image */
+      /*
+        Let the JPEG library quantize the image.
+      */
       jpeg_info.quantize_colors=MagickTrue;
       jpeg_info.desired_number_of_colors=(int) StringToUnsignedLong(option);
     }
   option=GetImageOption(image_info,"jpeg:block-smoothing");
-  if (option != (const char *) NULL)
-    {
-      jpeg_info.do_block_smoothing=MagickFalse;
-      if (IsMagickTrue(option) != MagickFalse)
-        jpeg_info.do_block_smoothing=MagickTrue;
-    }
+  jpeg_info.do_block_smoothing=IsStringTrue(option);
+  jpeg_info.dct_method=JDCT_FLOAT;
   option=GetImageOption(image_info,"jpeg:dct-method");
   if (option != (const char *) NULL)
     switch (*option)
@@ -1169,20 +1178,40 @@ static Image *ReadJPEGImage(const ImageInfo *image_info,
       }
     }
   option=GetImageOption(image_info,"jpeg:fancy-upsampling");
-  if (option != (const char *) NULL)
-    {
-      jpeg_info.do_fancy_upsampling=MagickFalse;
-      if (IsMagickTrue(option) != MagickFalse)
-        jpeg_info.do_fancy_upsampling=MagickTrue;
-    }
+  jpeg_info.do_fancy_upsampling=IsStringTrue(option);
   (void) jpeg_start_decompress(&jpeg_info);
   image->columns=jpeg_info.output_width;
   image->rows=jpeg_info.output_height;
   image->depth=(size_t) jpeg_info.data_precision;
-  if (jpeg_info.out_color_space == JCS_YCbCr)
-    image->colorspace=YCbCrColorspace;
-  if (jpeg_info.out_color_space == JCS_CMYK)
-    image->colorspace=CMYKColorspace;
+  switch (jpeg_info.out_color_space)
+  {
+    case JCS_RGB:
+    default:
+    {
+      SetImageColorspace(image,sRGBColorspace,exception);
+      break;
+    }
+    case JCS_GRAYSCALE:
+    {
+      SetImageColorspace(image,GRAYColorspace,exception);
+      break;
+    }
+    case JCS_YCbCr:
+    {
+      SetImageColorspace(image,YCbCrColorspace,exception);
+      break;
+    }
+    case JCS_CMYK:
+    {
+      SetImageColorspace(image,CMYKColorspace,exception);
+      break;
+    }
+  }
+  if (IsITUFaxImage(image) != MagickFalse)
+    {
+      SetImageColorspace(image,LabColorspace,exception);
+      jpeg_info.out_color_space=JCS_YCbCr;
+    }
   option=GetImageOption(image_info,"jpeg:colors");
   if (option != (const char *) NULL)
     if (AcquireImageColormap(image,StringToUnsignedLong(option),exception)
@@ -1246,7 +1275,8 @@ static Image *ReadJPEGImage(const ImageInfo *image_info,
       if (jpeg_info.out_color_space == JCS_GRAYSCALE)
         for (i=0; i < (ssize_t) image->colors; i++)
         {
-          image->colormap[i].red=ScaleCharToQuantum(jpeg_info.colormap[0][i]);
+          image->colormap[i].red=(double) ScaleCharToQuantum(
+            jpeg_info.colormap[0][i]);
           image->colormap[i].green=image->colormap[i].red;
           image->colormap[i].blue=image->colormap[i].red;
           image->colormap[i].alpha=OpaqueAlpha;
@@ -1254,9 +1284,12 @@ static Image *ReadJPEGImage(const ImageInfo *image_info,
       else
         for (i=0; i < (ssize_t) image->colors; i++)
         {
-          image->colormap[i].red=ScaleCharToQuantum(jpeg_info.colormap[0][i]);
-          image->colormap[i].green=ScaleCharToQuantum(jpeg_info.colormap[1][i]);
-          image->colormap[i].blue=ScaleCharToQuantum(jpeg_info.colormap[2][i]);
+          image->colormap[i].red=(double) ScaleCharToQuantum(
+            jpeg_info.colormap[0][i]);
+          image->colormap[i].green=(double) ScaleCharToQuantum(
+            jpeg_info.colormap[1][i]);
+          image->colormap[i].blue=(double) ScaleCharToQuantum(
+            jpeg_info.colormap[2][i]);
           image->colormap[i].alpha=OpaqueAlpha;
         }
     }
@@ -1523,6 +1556,19 @@ ModuleExport void UnregisterJPEGImage(void)
 %
 */
 
+static QuantizationTable *DestroyQuantizationTable(QuantizationTable *table)
+{
+  assert(table != (QuantizationTable *) NULL);
+  if (table->slot != (char *) NULL)
+    table->slot=DestroyString(table->slot);
+  if (table->description != (char *) NULL)
+    table->description=DestroyString(table->description);
+  if (table->levels != (unsigned int *) NULL)
+    table->levels=(unsigned int *) RelinquishMagickMemory(table->levels);
+  table=(QuantizationTable *) RelinquishMagickMemory(table);
+  return(table);
+}
+
 static boolean EmptyOutputBuffer(j_compress_ptr cinfo)
 {
   DestinationManager
@@ -1537,6 +1583,203 @@ static boolean EmptyOutputBuffer(j_compress_ptr cinfo)
   return(TRUE);
 }
 
+static QuantizationTable *GetQuantizationTable(const char *filename,
+  const char *slot,ExceptionInfo *exception)
+{
+  char
+    *p,
+    *xml;
+
+  const char
+    *attribute,
+    *content;
+
+  double
+    value;
+
+  register ssize_t
+    i;
+
+  ssize_t
+    j;
+
+  QuantizationTable
+    *table;
+
+  size_t
+    length;
+
+  XMLTreeInfo
+    *description,
+    *levels,
+    *quantization_tables,
+    *table_iterator;
+
+  (void) LogMagickEvent(ConfigureEvent,GetMagickModule(),
+    "Loading quantization tables \"%s\" ...",filename);
+  table=(QuantizationTable *) NULL;
+  xml=FileToString(filename,~0,exception);
+  if (xml == (char *) NULL)
+    return(table);
+  quantization_tables=NewXMLTree(xml,exception);
+  if (quantization_tables == (XMLTreeInfo *) NULL)
+    {
+      xml=DestroyString(xml);
+      return(table);
+    }
+  for (table_iterator=GetXMLTreeChild(quantization_tables,"table");
+       table_iterator != (XMLTreeInfo *) NULL;
+       table_iterator=GetNextXMLTreeTag(table_iterator))
+  {
+    attribute=GetXMLTreeAttribute(table_iterator,"slot");
+    if ((attribute != (char *) NULL) && (LocaleCompare(slot,attribute) == 0))
+      break;
+    attribute=GetXMLTreeAttribute(table_iterator,"alias");
+    if ((attribute != (char *) NULL) && (LocaleCompare(slot,attribute) == 0))
+      break;
+  }
+  if (table_iterator == (XMLTreeInfo *) NULL)
+    {
+      xml=DestroyString(xml);
+      return(table);
+    }
+  description=GetXMLTreeChild(table_iterator,"description");
+  if (description == (XMLTreeInfo *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingElement", "<description>, slot \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  levels=GetXMLTreeChild(table_iterator,"levels");
+  if (levels == (XMLTreeInfo *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingElement", "<levels>, slot \"%s\"", slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  table=(QuantizationTable *) AcquireMagickMemory(sizeof(*table));
+  if (table == (QuantizationTable *) NULL)
+    ThrowFatalException(ResourceLimitFatalError,
+      "UnableToAcquireQuantizationTable");
+  table->slot=(char *) NULL;
+  table->description=(char *) NULL;
+  table->levels=(unsigned int *) NULL;
+  attribute=GetXMLTreeAttribute(table_iterator,"slot");
+  if (attribute != (char *) NULL)
+    table->slot=ConstantString(attribute);
+  content=GetXMLTreeContent(description);
+  if (content != (char *) NULL)
+    table->description=ConstantString(content);
+  attribute=GetXMLTreeAttribute(levels,"width");
+  if (attribute == (char *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingAttribute", "<levels width>, slot \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  table->width=StringToUnsignedLong(attribute);
+  if (table->width == 0)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+       "XmlInvalidAttribute", "<levels width>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  attribute=GetXMLTreeAttribute(levels,"height");
+  if (attribute == (char *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingAttribute", "<levels height>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  table->height=StringToUnsignedLong(attribute);
+  if (table->height == 0)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlInvalidAttribute", "<levels height>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  attribute=GetXMLTreeAttribute(levels,"divisor");
+  if (attribute == (char *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingAttribute", "<levels divisor>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  table->divisor=InterpretLocaleValue(attribute,(char **) NULL);
+  if (table->divisor == 0.0)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlInvalidAttribute", "<levels divisor>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  content=GetXMLTreeContent(levels);
+  if (content == (char *) NULL)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlMissingContent", "<levels>, table \"%s\"",slot);
+      quantization_tables=DestroyXMLTree(quantization_tables);
+      table=DestroyQuantizationTable(table);
+      xml=DestroyString(xml);
+      return(table);
+    }
+  length=(size_t) table->width*table->height;
+  if (length < 64)
+    length=64;
+  table->levels=(unsigned int *) AcquireQuantumMemory(length,
+    sizeof(*table->levels));
+  if (table->levels == (unsigned int *) NULL)
+    ThrowFatalException(ResourceLimitFatalError,
+      "UnableToAcquireQuantizationTable");
+  for (i=0; i < (ssize_t) (table->width*table->height); i++)
+  {
+    table->levels[i]=(unsigned int) (InterpretLocaleValue(content,&p)/
+      table->divisor+0.5);
+    while (isspace((int) ((unsigned char) *p)) != 0)
+      p++;
+    if (*p == ',')
+      p++;
+    content=p;
+  }
+  value=InterpretLocaleValue(content,&p);
+  (void) value;
+  if (p != content)
+    {
+      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
+        "XmlInvalidContent", "<level> too many values, table \"%s\"",slot);
+     quantization_tables=DestroyXMLTree(quantization_tables);
+     table=DestroyQuantizationTable(table);
+     xml=DestroyString(xml);
+     return(table);
+   }
+  for (j=i; j < 64; j++)
+    table->levels[j]=table->levels[j-1];
+  quantization_tables=DestroyXMLTree(quantization_tables);
+  xml=DestroyString(xml);
+  return(table);
+}
+
 static void InitializeDestination(j_compress_ptr cinfo)
 {
   DestinationManager
@@ -1766,6 +2009,9 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
   ErrorManager
     error_manager;
 
+  int
+    quality;
+
   JSAMPLE
     *jpeg_pixels;
 
@@ -1859,8 +2105,8 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
     }
     default:
     {
-      if (IsRGBColorspace(image->colorspace) == MagickFalse)
-        (void) TransformImageColorspace(image,RGBColorspace,exception);
+      if (IssRGBCompatibleColorspace(image->colorspace) == MagickFalse)
+        (void) TransformImageColorspace(image,sRGBColorspace,exception);
       break;
     }
   }
@@ -1894,6 +2140,7 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
       if (image->units == PixelsPerCentimeterResolution)
         jpeg_info.density_unit=(UINT8) 2;
     }
+  jpeg_info.dct_method=JDCT_FLOAT;
   option=GetImageOption(image_info,"jpeg:dct-method");
   if (option != (const char *) NULL)
     switch (*option)
@@ -1926,11 +2173,7 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
     }
   option=GetImageOption(image_info,"jpeg:optimize-coding");
   if (option != (const char *) NULL)
-    {
-      jpeg_info.optimize_coding=MagickFalse;
-      if (IsMagickTrue(option) != MagickFalse)
-        jpeg_info.optimize_coding=MagickTrue;
-    }
+    jpeg_info.optimize_coding=IsStringTrue(option);
   else
     {
       MagickSizeType
@@ -1944,9 +2187,8 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
             Perform optimization only if available memory resources permit it.
           */
           status=AcquireMagickResource(MemoryResource,length);
-          if (status != MagickFalse)
-            jpeg_info.optimize_coding=MagickTrue;
           RelinquishMagickResource(MemoryResource,length);
+          jpeg_info.optimize_coding=status;
         }
     }
 #if (JPEG_LIB_VERSION >= 61) && defined(C_PROGRESSIVE_SUPPORTED)
@@ -2010,13 +2252,12 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
         }
       jpeg_info=DestroyImageInfo(jpeg_info);
     }
+  quality=92;
   if ((image_info->compression != LosslessJPEGCompression) &&
       (image->quality <= 100))
     {
-      if (image->quality == UndefinedCompressionQuality)
-        jpeg_set_quality(&jpeg_info,92,MagickTrue);
-      else
-        jpeg_set_quality(&jpeg_info,(int) image->quality,MagickTrue);
+      if (image->quality != UndefinedCompressionQuality)
+        quality=(int) image->quality;
       if (image->debug != MagickFalse)
         (void) LogMagickEvent(CoderEvent,GetMagickModule(),"Quality: %.20g",
           (double) image->quality);
@@ -2024,7 +2265,7 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
   else
     {
 #if !defined(C_LOSSLESS_SUPPORTED)
-      jpeg_set_quality(&jpeg_info,100,MagickTrue);
+      quality=100;
       if (image->debug != MagickFalse)
         (void) LogMagickEvent(CoderEvent,GetMagickModule(),"Quality: 100");
 #else
@@ -2052,8 +2293,35 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
         }
 #endif
     }
+  jpeg_set_quality(&jpeg_info,quality,MagickTrue);
+#if (JPEG_LIB_VERSION >= 70)
+  option=GetImageOption(image_info,"quality");
+  if (option != (const char *) NULL)
+    {
+      GeometryInfo
+        geometry_info;
+
+      int
+        flags;
+
+      /*
+        Set quality scaling for luminance and chrominance separately.
+      */
+      flags=ParseGeometry(option,&geometry_info);
+      if (((flags & RhoValue) != 0) && ((flags & SigmaValue) != 0))
+        {
+          jpeg_info.q_scale_factor[0]=jpeg_quality_scaling((int)
+            (geometry_info.rho+0.5));
+          jpeg_info.q_scale_factor[1]=jpeg_quality_scaling((int)
+            (geometry_info.sigma+0.5));
+          jpeg_default_qtables(&jpeg_info,MagickTrue);
+        }
+    }
+#endif
   sampling_factor=(const char *) NULL;
   value=GetImageProperty(image,"jpeg:sampling-factor",exception);
+  if (value == (char *) NULL)
+    value=GetImageOption(image_info,"jpeg:sampling-factor");
   if (value != (char *) NULL)
     {
       sampling_factor=value;
@@ -2115,6 +2383,44 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
       jpeg_info.comp_info[i].h_samp_factor=1;
       jpeg_info.comp_info[i].v_samp_factor=1;
     }
+  option=GetImageOption(image_info,"jpeg:q-table");
+  if (option != (const char *) NULL)
+    {
+      QuantizationTable
+        *table;
+
+      /*
+        Custom quantization tables.
+      */
+      table=GetQuantizationTable(option,"0",exception);
+      if (table != (QuantizationTable *) NULL)
+        {
+          jpeg_add_quant_table(&jpeg_info,0,table->levels,jpeg_quality_scaling(
+            quality),0);
+          table=DestroyQuantizationTable(table);
+        }
+      table=GetQuantizationTable(option,"1",exception);
+      if (table != (QuantizationTable *) NULL)
+        {
+          jpeg_add_quant_table(&jpeg_info,1,table->levels,jpeg_quality_scaling(
+            quality),0);
+          table=DestroyQuantizationTable(table);
+        }
+      table=GetQuantizationTable(option,"2",exception);
+      if (table != (QuantizationTable *) NULL)
+        {
+          jpeg_add_quant_table(&jpeg_info,2,table->levels,jpeg_quality_scaling(
+            quality),0);
+          table=DestroyQuantizationTable(table);
+        }
+      table=GetQuantizationTable(option,"3",exception);
+      if (table != (QuantizationTable *) NULL)
+        {
+          jpeg_add_quant_table(&jpeg_info,3,table->levels,jpeg_quality_scaling(
+            quality),0);
+          table=DestroyQuantizationTable(table);
+        }
+    }
   jpeg_start_compress(&jpeg_info,MagickTrue);
   if (image->debug != MagickFalse)
     {
@@ -2363,8 +2669,7 @@ static MagickBooleanType WriteJPEGImage(const ImageInfo *image_info,
         q=jpeg_pixels;
         for (x=0; x < (ssize_t) image->columns; x++)
         {
-          *q++=(JSAMPLE) (ScaleQuantumToShort(GetPixelIntensity(image,p)) >>
-            4);
+          *q++=(JSAMPLE) (ScaleQuantumToShort(GetPixelIntensity(image,p)) >> 4);
           p+=GetPixelChannels(image);
         }
         (void) jpeg_write_scanlines(&jpeg_info,scanline,1);