ASP.NET libwebp.dll 如何将 WebP 图像保存到磁盘

Question

我已经为 WebP 构建了 libwebp.dll，使用 these instructions (我下载了这个 source code )

我已将 libwebp.dll 文件添加到我项目的 bin 文件夹中。

然后我添加了这段代码(found here):

Private Declare Function WebPEncodeBGRA Lib "libwebp.dll" (ByVal rgba As IntPtr, ByVal width As Integer, ByVal height As Integer, ByVal stride As Integer, ByVal quality_factor As Single, ByRef output As IntPtr) As Integer
Private Declare Function WebPFree Lib "libwebp.dll" (ByVal p As IntPtr) As Integer

Private Sub Encode()
    Dim source As Bitmap = New Bitmap(Server.MapPath("images\") + "audio.png")
    Dim data As BitmapData = source.LockBits(New Rectangle(0, 0, source.Width, source.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb)
    Dim webp_data As IntPtr
    Dim i As Integer = WebPEncodeBGRA(data.Scan0, source.Width, source.Height, data.Stride, 80, webp_data)

    WebPFree(webp_data)
End Sub

我得到错误:

An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)

我也做了什么(在下面 Dai 的评论之后):

• 我为 64 位架构构建了 dll，如下所示:nmake/f Makefile.vc CFG=release-dynamic RTLIBCFG=dynamic OBJDIR=output ARCH=x64 ( also see here )<
• 我检查了 IIS 中有问题的应用程序池，它的属性 Enable32-Bit Applications 设置为 False
• 我运行的是 Windows 10 64 位
• 代码隐藏中的 Environment.Is64BitProcess 和 Environment.Is64BitOperatingSystem 都评估为 True

如何对图像进行编码并将编码后的图像以WebP格式保存到磁盘？

这是我正在使用的图像文件:

Answer 1

How can I encode the image and save the encoded image to disk in WebP format?

转换过程完成后，您需要整理非托管内存，以​​便您可以在托管代码中使用数据。

Public Sub Encode()
    Dim source As Bitmap = New Bitmap(Server.MapPath("images\audio.png"))
    'Hold bitmap data
    Dim bmpData As BitmapData = source.LockBits(New Rectangle(0, 0, source.Width, source.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb)

    'Create a pointer for webp data
    Dim webpDataSrc As IntPtr

    'Store resulting webp data length after conversion
    Dim webpDataLen As Integer = WebPEncodeBGRA(bmpData.Scan0, source.Width, source.Height, bmpData.Stride, 80, webpDataSrc)

    'Create a managed byte array with the size you just have
    Dim webpDataBin As Byte() = New Byte(webpDataLen - 1){}

    'Copy from unmanaged memory to managed byte array you created
    System.Runtime.InteropServices.Marshal.Copy(webpDataSrc, webpDataBin, 0, webpDataLen)

    'Write byte array to a file
    System.IO.File.WriteAllBytes(Server.MapPath("images\audio.webp"), webpDataBin)

    'Free
    WebPFree(webpDataSrc)

    source.Dispose()
End Sub

BTW 命令nmake/f Makefile.vc CFG=release-dynamic RTLIBCFG=dynamic OBJDIR=output ARCH=x64 你说你用的没问题。我也可以使用该命令编译库(版本 1.0.0)。但是我 100% 肯定 zipped libwebp.dll here是 32 位的，不是 64 位的。

确保启动正确的环境以生成 64 位二进制文​​件。