/// <summary>
/// 获取缩略图片
/// 指定当目标缩略图大于原图时 不处理
/// </summary>
/// <param name="original_image">原图</param>
/// <param name="titCase">缩图方式</param>
/// <param name="target_width">指定目标缩略图的宽度</param>
/// <param name="target_height">指定目标缩略图的高度</param>
/// <returns></returns>
public static Bitmap GetThumbnailImage(Image original_image, ThumbnailImageType titCase, int target_width, int target_height)
{
//原图高宽
int origin_width = original_image.Width, origin_height = original_image.Height;
float orignRatio = (float)origin_width / (float)origin_height; //原图 宽高 比例
int new_width = target_width, new_height = target_height; //新图片 宽高
float target_ratio = (float)target_width / (float)target_height;
//缩略图生成方式
switch (titCase)
{
//缩放全图到正确比例
case ThumbnailImageType.Zoom:
{
#region 缩图比例
if (target_width > 0 && target_height <= 0) //只有宽
{
new_height = (int)Math.Floor((float)target_width / orignRatio); //只有高
}
else if (target_height > 0 && target_width <= 0)
{
new_width = (int)Math.Floor((float)target_height * orignRatio);
}
else if (target_width > 0 && target_height > 0) //宽高同时限制
{
if (orignRatio > 1) //宽>高
{
new_height = (int)Math.Floor((float)target_width / orignRatio); //只有高
}
else
{
new_width = (int)Math.Floor((float)target_height * orignRatio);
}
}
#endregion
}
break;
}
// 创建缩略图
Bitmap returnImage = new System.Drawing.Bitmap(new_width, new_height);
System.Drawing.Graphics graphic = System.Drawing.Graphics.FromImage(returnImage);
//指定画布大小并以透明色填充空余部分
graphic.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.White), new System.Drawing.Rectangle(0, 0, new_width, new_height));
//设置高质量绘画
graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//输出缩略图
graphic.DrawImage(original_image, 0, 0, new_width, new_height);
return(returnImage);
}
/// <summary>
/// 指定大小简单等比缩放图片
/// </summary>
/// <param name="original_image"></param>
/// <param name="new_width"></param>
/// <returns></returns>
//public static Bitmap GetSimpleThumbnailImage(Image original_image, int new_width, int new_height)
//{
// NewImageSize imageSize = new NewImageSize(original_image.Width, original_image.Height, new_width, new_height);
// Bitmap returnImage = null;
// returnImage = new Bitmap(original_image, imageSize.NewWidth, imageSize.NewHeight);
// return returnImage;
//}
/// <summary>
/// 根据指定大小绘制高质量缩略图
/// </summary>
/// <param name="original_image"></param>
/// <param name="new_width"></param>
/// <returns></returns>
public static Bitmap GetThumbnailImage(Image original_image, ThumbnailImageType titCase, int target_width, int target_height)
{
System.Drawing.Graphics graphic = null;
Bitmap returnImage = null;
int origin_width = original_image.Width;
int origin_height = original_image.Height;
int paste_x = 0, paste_y = 0;
NewImageSize imageSize = new NewImageSize(original_image.Width, original_image.Height, target_width, target_height);
int new_width = imageSize.NewWidth, new_height = imageSize.NewHeight;
target_width = imageSize.NewWidth;
target_height = imageSize.NewHeight;
float origin_ratio = imageSize.OrignRatio;
float target_ratio = imageSize.NewRatio;
//缩略图生成方式
switch (titCase)
{
//缩放全图到正确比例
case ThumbnailImageType.Zoom:
if (target_ratio > origin_ratio)
{
//较宽图片
new_height = (int)Math.Floor((float)target_width / origin_ratio);
new_width = target_width;
}
else
{
//较高图片
new_height = target_height;
new_width = (int)Math.Floor(origin_ratio * (float)target_height);
}
new_width = new_width > target_width ? target_width : new_width;
new_height = new_height > target_height ? target_height : new_height;
break;
//截取高宽比中间部分
case ThumbnailImageType.Cut:
if (target_ratio > origin_ratio)
{
//较高图片
new_height = (int)Math.Floor((float)target_width / origin_ratio);
new_width = target_width;
}
else
{
//较宽图片
new_height = target_height;
new_width = (int)Math.Floor(origin_ratio * (float)target_height);
}
break;
}
paste_x = (target_width - new_width) / 2;
paste_y = (target_height - new_height) / 2;
// 创建缩略图
returnImage = new System.Drawing.Bitmap(target_width, target_height);
graphic = System.Drawing.Graphics.FromImage(returnImage);
//指定画布大小并以透明色填充空余部分
graphic.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.White), new System.Drawing.Rectangle(0, 0, target_width, target_height));
//设置高质量绘画
graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//输出缩略图
graphic.DrawImage(original_image, paste_x, paste_y, new_width, new_height);
return(returnImage);
}
