我有一个函数,用于改变图像的分辨率。我想这样做是为了将上传的图像(例如300dpi)修改为72dpi(用于web)。这个问题与另一个在SO上的问题(链接)相关,我正在处理这个问题。
我正在创建一个扩展方法,以便在我的应用程序中更多地使用此功能,而不仅仅是在上传新文件时使用(请参见上述提到的问题)。
提到的扩展方法正在类似下面情况的函数中被调用:
异常信息中的堆栈跟踪告诉我以下内容:
我正在创建一个扩展方法,以便在我的应用程序中更多地使用此功能,而不仅仅是在上传新文件时使用(请参见上述提到的问题)。
public static byte[] SetDpiTo72(this byte[] imageToFit, string mimeType, Size newSize)
{
using (MemoryStream memoryStream = new MemoryStream(), newMemoryStream = new MemoryStream())
{
memoryStream.Write(imageToFit, 0, imageToFit.Length);
var originalImage = new Bitmap(memoryStream);
using (var canvas = Graphics.FromImage(originalImage))
{
canvas.SmoothingMode = SmoothingMode.AntiAlias;
canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
canvas.DrawImage((Image)originalImage,0,0, newSize.Width, newSize.Height);
newBitmap.SetResolution(72, 72);
newBitmap.Save(newMemoryStream, ImageFunctions.GetEncoderInfo(mimeType), null);
}
return newMemoryStream.ToArray();
}
}
提到的扩展方法正在类似下面情况的函数中被调用:
if (newSize.Width > originalImage.Width && newSize.Height > originalImage.Height)
{
newSize.Width = originalImage.Width;
newSize.Height = originalImage.Height;
uploadedFileBuffer = uploadedFileBuffer.SetDpiTo72(uploadedFile.ContentType, newSize);
return CreateFile(newSize, uploadedFile, uploadedFileBuffer);
}
传入的bytearray是文件的字节数组。它已经具有正确的大小,但我想将分辨率更改为72dpi。然而,在执行并保存图像后,分辨率仍然是原始输入的300dpi。我该怎么做?
在几个答案之后更新:
public static byte[] SetDpiTo72(this byte[] imageToFit, string mimeType, Size newSize)
{
using (MemoryStream memoryStream = new MemoryStream(), newMemoryStream = new MemoryStream())
{
memoryStream.Write(imageToFit, 0, imageToFit.Length);
var originalImage = new Bitmap(memoryStream);
using (var canvas = Graphics.FromImage(originalImage))
{
canvas.SmoothingMode = SmoothingMode.AntiAlias;
canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
canvas.DrawImage((Image)originalImage,0,0, newSize.Width, newSize.Height);
originalImage.SetResolution(72, 72);
var epQuality = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 75);
var epParameters = new EncoderParameters(1);
epParameters.Param[0] = epQuality;
Image newimg = Image.FromStream(memoryStream);
//Getting an GDI+ exception after the execution of this line.
newimg.Save("C:\\test1234.jpg", ImageFunctions.GetEncoderInfo(mimeType), epParameters);
originalImage.Save("test.jpg", ImageFormat.Jpeg);
//This line give me an Argumentexception - Parameter is not valid.
//originalImage.Save(newMemoryStream, ImageFunctions.GetEncoderInfo(mimeType), epParameters);
//newMemoryStream.Close();
}
return newMemoryStream.ToArray();
}
}
异常信息中的堆栈跟踪告诉我以下内容:
at System.Drawing.Image.Save(String filename, ImageCodecInfo encoder, EncoderParameters encoderParams)
at Extensions.ByteArrayExtensions.SetDpiTo72(Byte[] imageToFit, String mimeType, Size newSize) in C:\Website\Project\Extensions\ByteArrayExtensions.cs:line 356
at CMS.Presentation.FileFunctions.CreateFullsizeImage(HttpPostedFileBase uploadedFile, Size newSize, Byte[] uploadedFileBuffer) in C:\Website\Project\CMS.Presentation\FileFunctions.cs:line 197
at CMS.Presentation.FileFunctions.CreateFile(HttpPostedFileBase uploadedFile, INodeService nodeservice, Guid userId, Node parentNode) in C:\Website\Project\CMS.Presentation\FileFunctions.cs:line 53
同时,我还开发了另一个函数(如下所示)来调整位图大小。这似乎能正常工作。然而,我不能在当前的实现中使用此函数,因为它仅返回位图。我是否应该更改所有内容以便与位图一起工作?
private static Bitmap ResizeImage(Image image, int width, int height)
{
var frameCount = image.GetFrameCount(new FrameDimension(image.FrameDimensionsList[0]));
var newDimensions = ImageFunctions.GenerateImageDimensions(image.Width, image.Height, width, height);
Bitmap resizedImage;
if (frameCount > 1)
{
//we have a animated GIF
resizedImage = ResizeAnimatedGifImage(image, width, height);
}
else
{
resizedImage = (Bitmap)image.GetThumbnailImage(newDimensions.Width, newDimensions.Height, null, IntPtr.Zero);
}
resizedImage.SetResolution(72,72);
return resizedImage;
}