C# 获取图片的大小和分辨率

C# 获取图片的大小和分辨率 [转贴 2011-4-20 13:39:19]






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文章来源: CSDN博客

//C#快速获取JPG图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#快速获取JPG图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) //文件结束
{
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; //加段长度

F_Stream.ReadByte(); //丢弃精度数据
//高度
JpgSize.Height = F_Stream.ReadByte() * 256;
JpgSize.Height = JpgSize.Height + F_Stream.ReadByte();
//宽度
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; //加段长度

F_Stream.Seek(5,SeekOrigin.Current); //丢弃APP0标记(5bytes)
F_Stream.Seek(2,SeekOrigin.Current); //丢弃主版本号(1bytes)及次版本号(1bytes)
int units=F_Stream.ReadByte(); //X和Y的密度单位,units=0：无单位,units=1：点数/英寸,units=2：点数/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); //厘米变为英寸
//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); //厘米变为英寸
//后面信息忽略
if (rx!=2 && rx<3) rx = rx + 2;
break;

default: //别的段都跳过////////////////
ps = F_Stream.ReadByte() * 256;
ps = F_Stream.Position + ps + F_Stream.ReadByte() - 2; //加段长度
break;
}
if (ps + 1 >= F_Stream.Length) //文件结束
{
F_Stream.Close();
return rx;
}
F_Stream.Position = ps; //移动指针
} while (type != 0xda); // 扫描行开始
F_Stream.Close();
return rx;
}

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