简介： 我有这个解决方案，包括一个Webapi应用程序，Winforms（UI）应用程序，然后是Xamarin Forms（Android，UWP，iOS）。
现在，调整大小和裁剪功能在Winforms的应用程序中有效。由于我在我的Webapi应用PerformInitSetup()中使用初始化数据，我还想在此处应用缩略图生成功能。
这些是方法（放在每个应用程序的帮助器类中）：
public static Image CropImage(Image img, Rectangle cropArea)
{
Bitmap bmpImage = new Bitmap(img);
Bitmap bmpCrop = bmpImage.Clone(cropArea,
bmpImage.PixelFormat);
return (Image)(bmpCrop);
}
public static Image ResizeImage(Image imgToResize, Size size)
{
int sourceWidth = imgToResize.Width;
int sourceHeight = imgToResize.Height;
float nPercent = 0;
float nPercentW = 0;
float nPercentH = 0;
nPercentW = ((float)size.Width / (float)sourceWidth);
nPercentH = ((float)size.Height / (float)sourceHeight);
if (nPercentH < nPercentW)
nPercent = nPercentH;
else
nPercent = nPercentW;
int destWidth = (int)(sourceWidth * nPercent);
int destHeight = (int)(sourceHeight * nPercent);
Bitmap b = new Bitmap(destWidth, destHeight);
Graphics g = Graphics.FromImage((Image)b);
g.InterpolationMode = InterpolationMode.HighQualityBicubic;
g.DrawImage(imgToResize, 0, 0, destWidth, destHeight);
g.Dispose();
return (Image)b;
}
在Winforms应用程序（确实有效）中，这里是如何保存常规图像，然后是基于它生成的缩略图：
private void btnAddImage_Click(object sender, EventArgs e)
{
if (openFileDialog.ShowDialog() == DialogResult.OK)
{
txtImage.Text = openFileDialog.FileName;
Image originalImage = Image.FromFile(openFileDialog.FileName);
MemoryStream ms = new MemoryStream();
originalImage.Save(ms, ImageFormat.Jpeg);
lodging.Image = ms.ToArray();
int resizedImageWidth = Convert.ToInt32(ConfigurationManager.AppSettings["resizedImageWidth"]);
int resizedImageHeight = Convert.ToInt32(ConfigurationManager.AppSettings["resizedImageHeight"]);
int croppedImageWidth = Convert.ToInt32(ConfigurationManager.AppSettings["croppedImageWidth"]);
int croppedImageHeight = Convert.ToInt32(ConfigurationManager.AppSettings["croppedImageHeight"]);
if(originalImage.Width > resizedImageWidth)
{
Image resizedImage = Util.UIHelper.ResizeImage(originalImage, new Size(resizedImageWidth, resizedImageHeight));
Image croppedImage = resizedImage;
if(resizedImage.Width >= croppedImageWidth && resizedImage.Height >= croppedImageHeight)
{
int croppedXPos = (resizedImageWidth - croppedImageWidth) / 2;
int croppedYPos = (resizedImageHeight - croppedImageHeight) / 2;
croppedImage = Util.UIHelper.CropImage(resizedImage, new Rectangle(croppedXPos, croppedYPos, croppedImageWidth, croppedImageHeight));
ms = new MemoryStream();
croppedImage.Save(ms, ImageFormat.Jpeg);
lodging.ImageThumb = ms.ToArray();
}
}
}
}
到目前为止，非常好。
但是当我尝试在Webapi应用程序的PerformInitSetup()方法中执行相同操作时，我收到错误（在底部找到它）：
// ... other init data
MemoryStream ms1 = new MemoryStream();
Image img1 = Image.FromFile("D:\\Path\\To\\MyImage\\image.jpg");
img1.Save(ms1, ImageFormat.Jpeg);
MemoryStream img1Thumb = GenerateThumbnailImage(img1);
_ctx.LodgingDbSet.Add(new Lodging { Name = "Name Name", ... other attributes ... , Image = ms1.ToArray(), ImageThumb = img1Thumb.ToArray(), CityId = 1, UserId = 2 });
// ... other init data
在InitDB : DropCreateDatabaseIfModelChanges<MyDbContext>方法的PerformInitSetup()类中，我有：
private MemoryStream GenerateThumbnailImage(Image originalImage)
{
int resizedImageWidth = Convert.ToInt32(ConfigurationManager.AppSettings["resizedImageWidth"]);
int resizedImageHeight = Convert.ToInt32(ConfigurationManager.AppSettings["resizedImageHeight"]);
int croppedImageWidth = Convert.ToInt32(ConfigurationManager.AppSettings["croppedImageWidth"]);
int croppedImageHeight = Convert.ToInt32(ConfigurationManager.AppSettings["croppedImageHeight"]);
MemoryStream ms = new MemoryStream();
if (originalImage.Width > resizedImageWidth)
{
Image resizedImage = Util.Helper.ResizeImage(originalImage, new Size(resizedImageWidth, resizedImageHeight));
Image croppedImage = resizedImage;
if (resizedImage.Width >= croppedImageWidth && resizedImage.Height >= croppedImageHeight)
{
int croppedXPos = (resizedImageWidth - croppedImageWidth) / 2;
int croppedYPos = (resizedImageHeight - croppedImageHeight) / 2;
croppedImage = Util.Helper.CropImage(
resizedImage,
new Rectangle(croppedXPos, croppedYPos, croppedImageWidth, croppedImageHeight)
);
croppedImage.Save(ms, ImageFormat.Jpeg);
}
}
return ms;
}
我认为这会奏效。然而，有些事情是错误的，但不幸的是，由于某种原因，断点似乎不能在这个MyDbContext文件中工作（对其解释会很感激！），所以我收到了这个错误：
{"Message":
"An error has occurred.",
"ExceptionMessage":
"Parameter is not valid.",
"ExceptionType":"System.ArgumentException",
"StackTrace":
" at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)\r\n
at System.Drawing.Bitmap..ctor(Int32 width, Int32 height)\r\n
at My_API.Util.Helper.ResizeImage(Image imgToResize, Size size) in D:\\Path\\To\\MyApp\\My_API\\Util\\Helper.cs:line 42\r\n
at My_API.DAL.InitDb.GenerateThumbnailImage(Image originalImage) in D:\\Path\\To\\MyApp\\My_API\\DAL\\MyDbContext.cs:line 341\r\n
at My_API.DAL.InitDb.PerformInitSetup(MyDbContext _ctx) in D:\\Path\\To\\MyApp\\My_API\\DAL\\MyDbContext.cs:line 176\r\n
at My_API.DAL.InitDb.Seed(MyDbContext _ctx) in D:\\Path\\To\\MyApp\\My_API\\DAL\\MyDbContext.cs:line 67\r\n
at System.Data.Entity.DropCreateDatabaseIfModelChanges`1.InitializeDatabase(TContext context)\r\n
// ... more stuff follows
上述方法的传递Image对象似乎不正确。但是，IMO，它与Winforms应用程序示例中的相同。
我错过了一些明显的东西吗？
编辑：正如评论中所建议的那样，我也提供了我的Web.config内容：
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<configSections>
<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</configSections>
<connectionStrings>
<add name="MyConnString" connectionString="Data Source=(local);Initial Catalog=mycatalog;Integrated Security=SSPI;MultipleActiveResultSets=true" providerName="System.Data.SqlClient" />
</connectionStrings>
<appSettings></appSettings>
<system.web>
<compilation debug="true" targetFramework="4.5.2" />
<httpRuntime targetFramework="4.5.2" />
</system.web>
<system.webServer>
<handlers>
<remove name="ExtensionlessUrlHandler-Integrated-4.0" />
<remove name="OPTIONSVerbHandler" />
<remove name="TRACEVerbHandler" />
<add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
</handlers>
</system.webServer>
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
<bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-10.0.0.0" newVersion="10.0.0.0" />
</dependentAssembly>
</assemblyBinding>
</runtime>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="mssqllocaldb" />
</parameters>
</defaultConnectionFactory>
<providers>
<provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
</providers>
</entityFramework>
<system.codedom>
<compilers>
<compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.7.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" />
<compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.7.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\"Web\" /optionInfer+" />
</compilers>
</system.codedom>
</configuration>
答案 0 :(得分：0)
最可能的原因是您尚未在web.config中定义这些设置：
resizedImageWidth
resizedImageHeight
croppedImageWidth
croppedImageHeight