所以我的逻辑存在缺陷，我需要一种更好更正确的方法来调整c＃app中的图像大小
我需要一个类似于此设置的功能
public void ResizeImageForWeb(string OriginalFile, string NewFile, int MaxWidth, int MaxHeight, int Quality)
{
// Resize Code
}
基本上，我是一名网页设计师，试图编写桌面应用程序。
答案 0 :(得分：8)
这是我用来调整用户上传的图片的代码，用于创建缩略图或仅强制执行尺寸限制。它没有解决图像质量问题，但它是一个开始。
// uses System.Drawing namespace
public class ImageResizer
{
public bool ResizeImage(string fullFileName, int maxHeight, int maxWidth)
{
return this.ResizeImage(fullFileName, maxHeight, maxWidth, fullFileName);
}
public bool ResizeImage(string fullFileName, int maxHeight, int maxWidth, string newFileName)
{
using (Image originalImage = Image.FromFile(fullFileName))
{
int height = originalImage.Height;
int width = originalImage.Width;
int newHeight = maxHeight;
int newWidth = maxWidth;
if (height > maxHeight || width > maxWidth)
{
if (height > maxHeight)
{
newHeight = maxHeight;
float temp = ((float)width / (float)height) * (float)maxHeight;
newWidth = Convert.ToInt32(temp);
height = newHeight;
width = newWidth;
}
if (width > maxWidth)
{
newWidth = maxWidth;
float temp = ((float)height / (float)width) * (float)maxWidth;
newHeight = Convert.ToInt32(temp);
}
Image.GetThumbnailImageAbort abort = new Image.GetThumbnailImageAbort(ThumbnailCallback);
using (Image resizedImage = originalImage.GetThumbnailImage(newWidth, newHeight, abort, System.IntPtr.Zero))
{
resizedImage.Save(newFileName);
}
return true;
}
else if (fullFileName != newFileName)
{
// no resizing necessary, but need to create new file
originalImage.Save(newFileName);
}
}
return false;
}
private bool ThumbnailCallback()
{
return false;
}
}
答案 1 :(得分：5)
我肯定不会使用GetThumbnailImage，因为它会让人感到震惊 - 如果不使用DX或OpenL等获得良好的分辨率，我会使用类似下面的内容（来自我在许多Windows应用程序中使用的图形库 - 我已经共享这之前有几次，所以可能有变量漂浮在网上）。这里有3种方法 - GetNonIndexedPixelFormat方法用于在传递无法处理的像素格式时停止GDI崩溃（注释解释）。第一个允许按因子缩放（缩放），最后一个允许固定大小重新缩放，同时保持纵横比（但如果你想改变它，可以很容易地修改）。享受：
/// <summary>
/// Scale Image By A Percentage - Scale Factor between 0 and 1.
/// </summary>
/// <param name="originalImg">Image: Image to scale</param>
/// <param name="ZoomFactor">Float: Sclae Value - 0 to 1 are the usual values</param>
/// <returns>Image: Scaled Image</returns>
public static Image ScaleByPercent(Image originalImg, float ZoomFactor)
{
int destWidth = (int)((float)originalImg.Width * ZoomFactor);
int destHeight = (int)((float)originalImg.Height * ZoomFactor);
Bitmap bmPhoto = new Bitmap(destWidth, destHeight, GetNonIndexedPixelFormat(originalImg)); // PixelFormat.Format24bppRgb);
bmPhoto.SetResolution(originalImg.HorizontalResolution, originalImg.VerticalResolution);
Graphics grPhoto = Graphics.FromImage(bmPhoto);
grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;
grPhoto.DrawImage(originalImg,
new Rectangle(0, 0, destWidth, destHeight),
new Rectangle(0, 0, originalImg.Width, originalImg.Height),
GraphicsUnit.Pixel);
grPhoto.Dispose();
return bmPhoto;
}
/// <summary>
/// Gets the closest non-indexed pixel format
/// </summary>
/// <param name="originalImage">Image: Original image</param>
/// <returns>PixelFormat: Closest non-pixel image format</returns>
public static PixelFormat GetNonIndexedPixelFormat(Image originalImage)
{
/*
* These formats cause an error when creating a GDI Graphics Oblect, so must be converted to non Indexed
* Error is "A graphics object cannot be created from an image that has an indexed pixel format"
*
PixelFormat.Undefined
PixelFormat.DontCare
PixelFormat.1bppIndexed
PixelFormat.4bppIndexed
PixelFormat.8bppIndexed
PixelFormat.16bppGrayScale
PixelFormat.16bppARGB1555
*
* An attempt is made to use the closest (i.e. smallest fitting) format that will hold the palette.
*/
switch (originalImage.PixelFormat)
{
case PixelFormat.Undefined:
//This is also the same Enumation as PixelFormat.DontCare:
return PixelFormat.Format24bppRgb;
case PixelFormat.Format1bppIndexed:
return PixelFormat.Format16bppRgb555;
case PixelFormat.Format4bppIndexed:
return PixelFormat.Format16bppRgb555;
case PixelFormat.Format8bppIndexed:
return PixelFormat.Format16bppRgb555;
case PixelFormat.Format16bppGrayScale:
return PixelFormat.Format16bppArgb1555;
case PixelFormat.Format32bppArgb:
return PixelFormat.Format24bppRgb;
default:
return originalImage.PixelFormat;
}
}
/// <summary>
/// Resize image keeping aspect ratio.
/// </summary>
/// <param name="originalImg">Image: Image to scale</param>
/// <param name="Width">Int: Required width in pixels</param>
/// <param name="Height">Int: Required height in pixels</param>
/// <param name="BackgroundColour">Color: Background colour</param>
/// <returns>Image: Scaled Image</returns>
public static Image Resize(Image originalImg, int Width, int Height, Color BackgroundColour)
{
int destX = 0;
int destY = 0;
float nPercent = 0f;
float nPercentW = ((float)Width / (float)originalImg.Width);
float nPercentH = ((float)Height / (float)originalImg.Height);
if (nPercentH < nPercentW)
{
nPercent = nPercentH;
destX = System.Convert.ToInt16(((float)Width - ((float)originalImg.Width * nPercent)) / 2f);
}
else
{
nPercent = nPercentW;
destY = System.Convert.ToInt16(((float)Height - ((float)originalImg.Height * nPercent)) / 2f);
}
int destWidth = (int)(originalImg.Width * nPercent);
int destHeight = (int)(originalImg.Height * nPercent);
Bitmap bmPhoto = new Bitmap(Width, Height, GetNonIndexedPixelFormat(originalImg)); // PixelFormat.Format24bppRgb);
bmPhoto.SetResolution(originalImg.HorizontalResolution, originalImg.VerticalResolution);
Graphics grPhoto = Graphics.FromImage(bmPhoto);
grPhoto.Clear(BackgroundColour);
grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;
grPhoto.DrawImage(originalImg,
new Rectangle(destX, destY, destWidth, destHeight),
new Rectangle(0, 0, originalImg.Width, originalImg.Height), GraphicsUnit.Pixel);
grPhoto.Dispose();
return bmPhoto;
}
答案 2 :(得分：2)
使用Graphics.DrawImage（）。 GetThumbnailImage（）将从jpeg文件返回一个120x120（或更小）的嵌入式缩略图。对于那么大的东西，这将是可怕的。
请参阅http://nathanaeljones.com/163/20-image-resizing-pitfalls/了解要使用的相应设置。
答案 3 :(得分：-1)
Google快速搜索发现这个小snippet。