public override void Init(Stream stream)
{
using (var bh = new ByteHelper(stream))
{
bh.Seek(0, SeekOrigin.Begin);
// https://en.wikipedia.org/wiki/BMP_file_format
IsValid = bh.ReadAscii(2) == "BM";
if (!IsValid)
{
return;
}
bh.Seek(18, SeekOrigin.Begin);
Width = (int)bh.ReadUint();
Height = (int)bh.ReadUint();
bh.Seek(38, SeekOrigin.Begin);
var pixelsPerMeterH = (int)bh.ReadUint();
DpiH = PixelsPerMeterToPixelsPerInch(pixelsPerMeterH);
var pixelsPerMeterV = (int)bh.ReadUint();
DpiV = PixelsPerMeterToPixelsPerInch(pixelsPerMeterV);
}
}
public override void Init(Stream stream)
{
using (var bh = new ByteHelper(stream))
{
bh.IsLsbf = false;
bh.Seek(0, SeekOrigin.Begin);
// http://www.libpng.org/pub/png/spec/1.2/PNG-Structure.html
var signature = bh.ReadBytes(8);
IsValid = signature[0] == 137 && signature[1] == 80 && signature[2] == 78 && signature[3] == 71 &&
signature[4] == 13 && signature[5] == 10 && signature[6] == 26 && signature[7] == 10;
if (!IsValid)
{
return;
}
DpiH = DpiV = 96;
while (stream.Position < stream.Length)
{
var chunkDataLength = bh.ReadUint();
var chunkType = bh.ReadAscii(4);
switch (chunkType)
{
case "IHDR":
Width = (int)bh.ReadUint();
Height = (int)bh.ReadUint();
bh.Seek(5);
break;
case "pHYs":
var pixelsPerUnitX = (int)bh.ReadUint();
var pixelsPerUnitY = (int)bh.ReadUint();
var unit = bh.ReadByte();
if (unit == 1)
{
// Unit is the meter.
DpiH = PixelsPerMeterToPixelsPerInch(pixelsPerUnitX);
DpiV = PixelsPerMeterToPixelsPerInch(pixelsPerUnitY);
}
return;
default:
bh.Seek(chunkDataLength, SeekOrigin.Current);
break;
}
// Skip CRC.
bh.Seek(4, SeekOrigin.Current);
}
}
}
public override void Init(Stream stream)
{
ushort resolutionUnit = 0;
using (var bh = new ByteHelper(stream))
{
bh.Seek(0, SeekOrigin.Begin);
var byteOrder = bh.ReadAscii(2);
if (byteOrder != "II" && byteOrder != "MM")
{
return;
}
bh.IsLsbf = byteOrder == "II";
bh.Seek(2);
var ifdOffset = bh.ReadUint();
bh.Seek(ifdOffset, SeekOrigin.Begin);
var entryCount = bh.ReadUshort();
for (ushort i = 0; i < entryCount; ++i)
{
var entryTag = bh.ReadUshort();
var fieldType = bh.ReadUshort();
var numberOfComponents = bh.ReadUint();
switch (entryTag)
{
case (int)Tags.ImageWidth:
switch (fieldType)
{
case (ushort)FieldTypes.Short:
Width = bh.ReadUshort();
bh.Seek(2);
break;
case (ushort)FieldTypes.Long:
Width = (int)bh.ReadUint();
break;
}
break;
case (int)Tags.ImageHeight:
switch (fieldType)
{
case (ushort)FieldTypes.Short:
Height = bh.ReadUshort();
bh.Seek(2);
break;
case (ushort)FieldTypes.Long:
Height = (int)bh.ReadUint();
break;
}
break;
case (int)Tags.XResolution:
{
// Field type is always rational.
var tagDataOffset = bh.ReadUint();
var currentOffset = stream.Position;
stream.Seek(tagDataOffset, SeekOrigin.Begin);
var numerator = bh.ReadUint();
var denominator = bh.ReadUint();
DpiH = (int)Math.Round((double)numerator / denominator);
stream.Seek(currentOffset, SeekOrigin.Begin);
break;
}
case (int)Tags.YResolution:
{
// Field type is always rational.
var tagDataOffset = bh.ReadUint();
var currentOffset = stream.Position;
stream.Seek(tagDataOffset, SeekOrigin.Begin);
var numerator = bh.ReadUint();
var denominator = bh.ReadUint();
DpiV = (int)Math.Round((double)numerator / denominator);
stream.Seek(currentOffset, SeekOrigin.Begin);
break;
}
case (int)Tags.ResolutionUnit:
resolutionUnit = bh.ReadUshort();
bh.Seek(2);
break;
default:
bh.Seek(4);
break;
}
}
}
// https://www.awaresystems.be/imaging/tiff/tifftags/resolutionunit.html
if (resolutionUnit == 0 || resolutionUnit == 1)
{
DpiH = DpiV = 72;
}
else if (resolutionUnit == 3)
{
DpiH = PixelsPerMeterToPixelsPerInch(DpiH * 100);
DpiV = PixelsPerMeterToPixelsPerInch(DpiV * 100);
}
IsValid = true;
}