[转]图片处理函数（自适应缩略图datatable中添加缩略图像）

/// <summary>
/// 为DataTable指定行中的生成缩略图
/// </summary>
/// <param name="dataTable">数据源</param>
/// <param name="dataTableImageColumnName">要生成缩略图的数据源的列名</param>
/// <param name="appendSmallPicColumnName">新增缩略图数据列的列名</param>
/// <param name="imageFormat">源图像格式</param>
/// <param name="maxWidth">图像自适应的最大宽度</param>
/// <param name="maxHeight">最像自适应的最大高度</param>
public static void GetSmallPic(DataTable dataTable, string dataTableImageColumnName, string appendSmallPicColumnName, ImageFormat imageFormat, int maxWidth, int maxHeight)
{
var dc = new DataColumn(appendSmallPicColumnName, Type.GetType("System.Byte[]"));
dataTable.Columns.Add(dc);
for (int i = 0; i < dataTable.Rows.Count; i++)
{
//生成缩略图GetSmallPic(dataTable.Rows[i], dataTableImageColumnName, appendSmallPicColumnName);
var imageByte = (byte[])dataTable.Rows[i][dataTableImageColumnName];
var ms = new MemoryStream(imageByte, 0, imageByte.Length);
var sourceImage = Image.FromStream(ms);
int newWidth, newHeight;
ImageSelfAdaption(sourceImage, maxWidth, maxHeight, out newWidth, out newHeight);
var myBitmap = new Bitmap(sourceImage, newWidth, newHeight);
ms = new MemoryStream();
myBitmap.Save(ms, imageFormat);
dataTable.Rows[i][appendSmallPicColumnName] = ms.ToArray();
ms.Close();
}
}

/// <summary>
/// 获取图像自适应后的宽高（设置最大宽高）
/// </summary>
/// <param name="image">图像</param>
/// <param name="maxWidth">最大宽度</param>
/// <param name="maxHeight">最大高度</param>
/// <param name="newWidth">自适应后的图像宽度</param>
/// <param name="newHeight">自适应后的图像高度</param>
/// <returns></returns>
public static void ImageSelfAdaption(Image image, int maxWidth, int maxHeight, out int newWidth, out int newHeight)
{
var originalWidth = image.Width;
var originalHeight = image.Height;
double _newWidth = maxWidth, _newHeight = maxHeight;
double t = originalWidth > maxWidth ? maxWidth : originalWidth;
if (originalHeight * t / originalWidth > maxHeight)
{
_newHeight = maxHeight;
_newWidth = (double)maxHeight / originalHeight * originalWidth;
}
else
{
_newWidth = t;
_newHeight = (t / originalWidth) * originalHeight;
}
newWidth = (int)_newWidth;
newHeight = (int)_newHeight;
}

/// <summary>
/// 获取补足透明区域的图像
/// </summary>
/// <param name="image">欲补足透明区域的图像</param>
/// <param name="minComplementSize">补足透明区域的最小像素块大小（注：必须大于等于2）</param>
/// <returns></returns>
public static Bitmap GetComplementImage(Image image, int minComplementSize)
{
if (minComplementSize < 2)
{
return new Bitmap(image.Width, image.Height);
}
else
{
int newWidth = image.Width;
int newHeight = image.Height;
//宽度求余
int width = image.Width % minComplementSize;
//高度求余
int height = image.Height % minComplementSize;
//宽度不够
if (width != 0)
{
newWidth += minComplementSize - width;
}
if (height != 0) //高度不够
{
newHeight += minComplementSize - height;
}
return new Bitmap(image, newWidth, newHeight);
}
}

/// <summary>
/// 获取图像对象
/// </summary>
/// <param name="imageByte">图像二进制数据</param>
/// <returns></returns>
public static Image GetImage(byte[] imageByte)
{
if (imageByte != null)
{
var ms = new MemoryStream();
ms.Write(imageByte, 0, imageByte.Length);
return Image.FromStream(ms);
}
return null;
}

/// <summary>
/// 获取图像二进制数据
/// </summary>
/// <param name="image">图像</param>
/// <param name="imageFormat">图像格式</param>
/// <returns></returns>
public static byte[] GetImageByteArray(Image image, ImageFormat imageFormat)
{
var ms = new MemoryStream();
image.Save(ms, imageFormat);
var img = new byte[ms.Length];
ms.Position = 0;
ms.Read(img, 0, Convert.ToInt32(ms.Length));
ms.Close();
return img;
}