毫秒级的时间处理上G的图片
测试环境：
测试图片（30M）：
测试计时方法：
Stopwatch sw1 = new Stopwatch(); sw1.Start(); //TODO...... sw1.Stop(); string xx = sw1.ElapsedMilliseconds.ToString(); MessageBox.Show(xx);
方法一，（1张30M图片，用时799毫秒）
public Image getThumbNailUsingGetThumbnailImage(string fileName)
{
Image img = Image.FromFile(fileName);
return img.GetThumbnailImage(300, 300, null, IntPtr.Zero);
}
方法二，（1张30M图片，用时1329毫秒）
public Image createThumbnailUsingGDI(ref Image imgPhoto, int destWidth, int destHeight)
{
int sourceX = 0;
int sourceY = 0;
int destX = 0;
int destY = 0;
int sourceWidth = imgPhoto.Width;
int sourceHeight = imgPhoto.Height;
Bitmap b = new Bitmap(destWidth, destHeight);
Graphics grPhoto = Graphics.FromImage(b);
grPhoto.FillRectangle(Brushes.DarkGray, new Rectangle(destX, destY, destWidth, destHeight));
grPhoto.DrawLine(new Pen(Brushes.LightGray), new Point(0, destHeight - 1), new Point(destWidth, destHeight - 1));
grPhoto.DrawLine(new Pen(Brushes.LightGray), new Point(destWidth - 1, 0), new Point(destWidth - 1, destHeight));
//shade right
grPhoto.FillRectangle(Brushes.White, new Rectangle(destWidth - 3, 0, 7, 2));
grPhoto.FillRectangle(Brushes.White, new Rectangle(destWidth - 2, 0, 7, 4));
grPhoto.FillRectangle(Brushes.White, new Rectangle(destWidth - 1, 0, 7, 6));
//shade botton
grPhoto.FillRectangle(Brushes.White, new Rectangle(0, destHeight - 3, 2, 7));
grPhoto.FillRectangle(Brushes.White, new Rectangle(0, destHeight - 2, 4, 7));
grPhoto.FillRectangle(Brushes.White, new Rectangle(0, destHeight - 1, 6, 7));
grPhoto.DrawImage(imgPhoto, new Rectangle(destX + 2, destY + 2, destWidth - 7, destHeight - 7), new Rectangle(sourceX, sourceY, sourceWidth, sourceHeight), GraphicsUnit.Pixel);
grPhoto.Dispose();
return b;
}
方法三，（1张30M图片，用时1636毫秒）
public Image getThumbNailWithFrame(string fileName)
{
FileStream fs = new FileStream(fileName, FileMode.Open);
Image im = Image.FromStream(fs);
Size szMax = new Size(300, 300);
Size sz = getProportionalSize(szMax, im.Size);
// superior image quality
Bitmap bmpResized = new Bitmap(sz.Width, sz.Height);
using (Graphics g = Graphics.FromImage(bmpResized))
{
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.FillRectangle(Brushes.White, 0, 0, sz.Width, sz.Height);
int FrameWidth = 5;//decides the frame border width
g.DrawRectangle(new Pen(Color.Silver, FrameWidth - 2), 0, 0, sz.Width - 1, sz.Height - 1);
FrameWidth += 5;//decide the frame width
g.DrawImage(im, new Rectangle(FrameWidth, FrameWidth, sz.Width - FrameWidth * 2, sz.Height - FrameWidth * 2), new Rectangle(Point.Empty, im.Size), GraphicsUnit.Pixel);
}
im.Dispose(); im = null;
fs.Close(); fs.Dispose(); fs = null;
return bmpResized;
}
private Size getProportionalSize(Size szMax, Size szReal)
{
int nWidth;
int nHeight;
double sMaxRatio;
double sRealRatio;
if (szMax.Width < 1 || szMax.Height < 1 || szReal.Width < 1 || szReal.Height < 1)
return Size.Empty;
sMaxRatio = (double)szMax.Width / (double)szMax.Height;
sRealRatio = (double)szReal.Width / (double)szReal.Height;
if (sMaxRatio < sRealRatio)
{
nWidth = Math.Min(szMax.Width, szReal.Width);
nHeight = (int)Math.Round(nWidth / sRealRatio);
}
else
{
nHeight = Math.Min(szMax.Height, szReal.Height);
nWidth = (int)Math.Round(nHeight * sRealRatio);
}
return new Size(nWidth, nHeight);
}
方法四，（1张30M图片，用时1664毫秒）
public Image getThumbNail(string fileName)
{
FileStream fs = new FileStream(fileName, FileMode.Open);
Image im = Image.FromStream(fs);
Size szMax = new Size(300, 300);
Size sz = getProportionalSize(szMax, im.Size);
// superior image quality
Bitmap bmpResized = new Bitmap(sz.Width, sz.Height);
using (Graphics g = Graphics.FromImage(bmpResized))
{
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(
im,
new Rectangle(Point.Empty, sz),
new Rectangle(Point.Empty, im.Size),
GraphicsUnit.Pixel);
}
im.Dispose(); im = null;
fs.Close(); fs.Dispose(); fs = null;
return bmpResized;
}
private Size getProportionalSize(Size szMax, Size szReal)
{
int nWidth;
int nHeight;
double sMaxRatio;
double sRealRatio;
if (szMax.Width < 1 || szMax.Height < 1 || szReal.Width < 1 || szReal.Height < 1)
return Size.Empty;
sMaxRatio = (double)szMax.Width / (double)szMax.Height;
sRealRatio = (double)szReal.Width / (double)szReal.Height;
if (sMaxRatio < sRealRatio)
{
nWidth = Math.Min(szMax.Width, szReal.Width);
nHeight = (int)Math.Round(nWidth / sRealRatio);
}
else
{
nHeight = Math.Min(szMax.Height, szReal.Height);
nWidth = (int)Math.Round(nHeight * sRealRatio);
}
return new Size(nWidth, nHeight);
}
方法五，（1张30M图片，用时735毫秒）
public Image createThumbFromProperty(string file)
{
Image image = new Bitmap(file);
Image Thumb = null;
PropertyItem[] propItems = image.PropertyItems;
foreach (PropertyItem propItem in propItems)
{
if (propItem.Id == 0x501B)
{
byte[] imageBytes = propItem.Value;
MemoryStream stream = new MemoryStream(imageBytes.Length);
stream.Write(imageBytes, 0, imageBytes.Length);
Thumb = Image.FromStream(stream);
break;
}
}
return Thumb;
}
方法六，（50张30M图片，237毫秒）
View Code
方法七，（50张30M图片，96毫秒）
速度最快，只要兄弟们推荐的多，我下午公布源码。^_^
测试结果：
| 方法 | 图片张数（张） | 每张大小（M） | 图片总大小 | 用时 |
| 方法一 | 50 | 30 | 1500M | 39950毫秒=40秒 |
| 方法二 | 50 | 30 | 1500M | 66450毫秒=66秒 |
| 方法三 | 50 | 30 | 1500M | 81800毫秒=81秒 |
| 方法四 | 50 | 30 | 1500M | 83200毫秒=83秒 |
| 方法五 | 50 | 30 | 1500M | 36750毫秒=37秒 |
| 方法六 | 50 | 30 | 1500M | 237毫秒 |
| 方法七 | 50 | 30 | 1500M | 96毫秒 |
