//C#快速獲取JPG圖片大小及英寸分辨率
public static int getJpgSize(string
FileName, out Size JpgSize, out float Wpx, out float Hpx)
{//C#快速獲取JPG圖片大小及英寸分辨率
JpgSize = new Size(0, 0);
Wpx = 0; Hpx = 0;
int rx = 0;
if
(!File.Exists(FileName)) return rx;
FileStream F_Stream =
File.OpenRead(FileName);
int ff =
F_Stream.ReadByte();
int type =
F_Stream.ReadByte();
if (ff != 0xff || type !=
0xd8)
{//非JPG文件
F_Stream.Close();
return rx;
}
long ps = 0;
do
{
do
{
ff =
F_Stream.ReadByte();
if (ff < 0)
//文件結束
{
F_Stream.Close();
return rx;
}
} while (ff != 0xff);
do
{
type =
F_Stream.ReadByte();
} while (type == 0xff);
//MessageBox.Show(ff.ToString() + "," + type.ToString(),
F_Stream.Position.ToString());
ps =
F_Stream.Position;
switch (type)
{
case 0x00:
case
0x01:
case 0xD0:
case
0xD1:
case 0xD2:
case
0xD3:
case 0xD4:
case
0xD5:
case 0xD6:
case
0xD7:
break;
case 0xc0:
//SOF0段
ps = F_Stream.ReadByte() *
256;
ps = F_Stream.Position + ps +
F_Stream.ReadByte() - 2; //加段長度
F_Stream.ReadByte();
//丟棄精度數據
//高度
JpgSize.Height = F_Stream.ReadByte() * 256;
JpgSize.Height = JpgSize.Height +
F_Stream.ReadByte();
//寬度
JpgSize.Width = F_Stream.ReadByte() * 256;
JpgSize.Width = JpgSize.Width + F_Stream.ReadByte();
//后面信息忽略
if (rx!=1 && rx < 3) rx = rx +
1;
break;
case 0xe0:
//APP0段
ps = F_Stream.ReadByte() *
256;
ps = F_Stream.Position + ps +
F_Stream.ReadByte() - 2; //加段長度
F_Stream.Seek(5,SeekOrigin.Current);
//丟棄APP0標記(5bytes)
F_Stream.Seek(2,SeekOrigin.Current);
//丟棄主版本號(1bytes)及次版本號(1bytes)
int
units=F_Stream.ReadByte();
//X和Y的密度單位,units=0：無單位,units=1：點數/英寸,units=2：點數/厘米
//水平方向(像素/英寸)分辨率
Wpx=F_Stream.ReadByte()*256;
Wpx=Wpx+F_Stream.ReadByte();
if (units == 2) Wpx =
(float)(Wpx * 2.54); //厘米變為英寸
//垂直方向(像素/英寸)分辨率
Hpx = F_Stream.ReadByte() *
256;
Hpx = Hpx +
F_Stream.ReadByte();
if (units == 2) Hpx =
(float)(Hpx * 2.54); //厘米變為英寸
//后面信息忽略
if (rx!=2 && rx<3) rx = rx +
2;
break;
default:
//別的段都跳過////////////////
ps = F_Stream.ReadByte() *
256;
ps = F_Stream.Position + ps +
F_Stream.ReadByte() - 2; //加段長度
break;
}
if (ps + 1 >= F_Stream.Length)
//文件結束
{
F_Stream.Close();
return rx;
}
F_Stream.Position = ps; //移動指針
} while (type
!= 0xda); // 掃描行開始
F_Stream.Close();
return
rx;
}