private bool MoveToNextHeader(StreamReaderHelper stream)
{
int blockLength = stream.GetWord(2, true);
int headerMagic = stream.GetByte(0);
int headerType = stream.GetByte(1);
if (headerMagic == 0xff)
{
// EOI: last header.
if (headerType == 0xd9)
{
return(false);
}
// Check for standalone markers.
if (headerType == 0x01 || headerType >= 0xd0 && headerType <= 0xd7)
{
stream.CurrentOffset += 2;
return(true);
}
// Now assume header with block size.
stream.CurrentOffset += 2 + blockLength;
return(true);
}
return(false);
}
private bool TestColorFormatHeader(StreamReaderHelper stream, ImportedImage ii)
{
// The SOS header (start of scan).
if (stream.GetWord(0, true) == 0xffda)
{
int components = stream.GetByte(4);
if (components < 1 || components > 4 || components == 2)
{
return(false);
}
// 1 for grayscale, 3 for RGB, 4 for CMYK.
int blockLength = stream.GetWord(2, true);
// Integrity check: correct size?
if (blockLength != 6 + 2 * components)
{
return(false);
}
// Eventually do more tests here.
// Magic: we assume that all JPEG files with 4 components are RGBW (inverted CMYK) and not CMYK.
// We add a test to tell CMYK from RGBW when we encounter a test file in CMYK format.
ii.Information.ImageFormat = components == 3 ? ImageInformation.ImageFormats.JPEG :
(components == 1 ? ImageInformation.ImageFormats.JPEGGRAY : ImageInformation.ImageFormats.JPEGRGBW);
return(true);
}
return(false);
}
private bool TestJfifHeader(StreamReaderHelper stream, ImportedImage ii)
{
// The App0 header should be the first header in every JFIF file.
if (stream.GetWord(0, true) == 0xffe0)
{
// Now check for text "JFIF".
if (stream.GetDWord(4, true) == 0x4a464946)
{
int blockLength = stream.GetWord(2, true);
if (blockLength >= 16)
{
int version = stream.GetWord(9, true);
int units = stream.GetByte(11);
int densityX = stream.GetWord(12, true);
int densityY = stream.GetWord(14, true);
switch (units)
{
case 0: // Aspect ratio only.
ii.Information.HorizontalAspectRatio = densityX;
ii.Information.VerticalAspectRatio = densityY;
break;
case 1: // DPI.
ii.Information.HorizontalDPI = densityX;
ii.Information.VerticalDPI = densityY;
break;
case 2: // DPCM.
ii.Information.HorizontalDPM = densityX * 100;
ii.Information.VerticalDPM = densityY * 100;
break;
}
// More information here? More tests?
return(true);
}
}
}
return(false);
}
private bool TestJfifHeader(StreamReaderHelper stream, ImportedImage ii)
{
// The App0 header should be the first header in every JFIF file.
if (stream.GetWord(0, true) == 0xffe0)
{
// Now check for text "JFIF".
if (stream.GetDWord(4, true) == 0x4a464946)
{
int blockLength = stream.GetWord(2, true);
if (blockLength >= 16)
{
int version = stream.GetWord(9, true);
int units = stream.GetByte(11);
int densityX = stream.GetWord(12, true);
int densityY = stream.GetWord(14, true);
switch (units)
{
case 0: // Aspect ratio only.
ii.Information.HorizontalAspectRatio = densityX;
ii.Information.VerticalAspectRatio = densityY;
break;
case 1: // DPI.
ii.Information.HorizontalDPI = densityX;
ii.Information.VerticalDPI = densityY;
break;
case 2: // DPCM.
ii.Information.HorizontalDPM = densityX * 100;
ii.Information.VerticalDPM = densityY * 100;
break;
}
// More information here? More tests?
return true;
}
}
}
return false;
}
private bool MoveToNextHeader(StreamReaderHelper stream)
{
int blockLength = stream.GetWord(2, true);
int headerMagic = stream.GetByte(0);
int headerType = stream.GetByte(1);
if (headerMagic == 0xff)
{
// EOI: last header.
if (headerType == 0xd9)
return false;
// Check for standalone markers.
if (headerType == 0x01 || headerType >= 0xd0 && headerType <= 0xd7)
{
stream.CurrentOffset += 2;
return true;
}
// Now assume header with block size.
stream.CurrentOffset += 2 + blockLength;
return true;
}
return false;
}
private bool TestColorFormatHeader(StreamReaderHelper stream, ImportedImage ii)
{
// The SOS header (start of scan).
if (stream.GetWord(0, true) == 0xffda)
{
int components = stream.GetByte(4);
if (components < 1 || components > 4 || components == 2)
return false;
// 1 for grayscale, 3 for RGB, 4 for CMYK.
int blockLength = stream.GetWord(2, true);
// Integrity check: correct size?
if (blockLength != 6 + 2 * components)
return false;
// Eventually do more tests here.
// Magic: we assume that all JPEG files with 4 components are RGBW (inverted CMYK) and not CMYK.
// We add a test to tell CMYK from RGBW when we encounter a test file in CMYK format.
ii.Information.ImageFormat = components == 3 ? ImageInformation.ImageFormats.JPEG :
(components == 1 ? ImageInformation.ImageFormats.JPEGGRAY : ImageInformation.ImageFormats.JPEGRGBW);
return true;
}
return false;
}