Question

我试图从随机数据中生成C＃中的16位灰度位图。但它在Marshal.Copy上崩溃。

这是我的代码：

   Bitmap b16bpp;
    private void GenerateDummy16bitImage()
    {

        b16bpp = new Bitmap(IMAGE_WIDTH, IMAGE_HEIGHT, System.Drawing.Imaging.PixelFormat.Format16bppGrayScale);

        var rect = new Rectangle(0, 0, IMAGE_WIDTH, IMAGE_HEIGHT);
        var bitmapData = b16bpp.LockBits(rect, ImageLockMode.WriteOnly, b16bpp.PixelFormat);
        // Calculate the number of bytes required and allocate them.
        var numberOfBytes = bitmapData.Stride * IMAGE_HEIGHT * 2;
        var bitmapBytes = new short[numberOfBytes];
        // Fill the bitmap bytes with random data.
        var random = new Random();
        for (int x = 0; x < IMAGE_WIDTH; x++)
        {
            for (int y = 0; y < IMAGE_HEIGHT; y++)
            {

                var i = ((y * IMAGE_WIDTH) + x) * 2; // 16bpp

                // Generate the next random pixel color value.
                var value = (short)random.Next(5);

                bitmapBytes[i] = value;         // BLUE
                bitmapBytes[i + 1] = value;     // GREEN
                bitmapBytes[i + 2] = value;     // RED
              //  bitmapBytes[i + 3] = 0xFF;      // ALPHA
            }
        }
        // Copy the randomized bits to the bitmap pointer.
        var ptr = bitmapData.Scan0;
        Marshal.Copy(bitmapBytes, 0, ptr, numberOfBytes);//crashes here

        // Unlock the bitmap, we're all done.
        b16bpp.UnlockBits(bitmapData);

        b16bpp.Save("random.bmp", ImageFormat.Bmp);
        Debug.WriteLine("saved");
    }

例外是：

未处理的类型＆＃39; System.AccessViolationException＆＃39;发生在mscorlib.dll

这不是我的代码。我发现它与32位Bitmaps和修改有关。但我想我错过了一些东西，因为我对C＃很新。

基本上，我需要的是将BitmapData包装成一个短裤数组。

Answer 1

这适用于System.Drawing.Imaging.PixelFormat.Format16bppGrayScale：

    private static void SaveBmp(Bitmap bmp, string path)
    {
        Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);

        BitmapData bitmapData = bmp.LockBits(rect, ImageLockMode.ReadOnly, bmp.PixelFormat);

        var pixelFormats = ConvertBmpPixelFormat(bmp.PixelFormat);

        BitmapSource source = BitmapSource.Create(bmp.Width,
                                                  bmp.Height,
                                                  bmp.HorizontalResolution,
                                                  bmp.VerticalResolution,
                                                  pixelFormats,
                                                  null,
                                                  bitmapData.Scan0,
                                                  bitmapData.Stride * bmp.Height,
                                                  bitmapData.Stride);

        bmp.UnlockBits(bitmapData);


        FileStream stream = new FileStream(path, FileMode.Create);

        TiffBitmapEncoder encoder = new TiffBitmapEncoder();

        encoder.Compression = TiffCompressOption.Zip;
        encoder.Frames.Add(BitmapFrame.Create(source));
        encoder.Save(stream);

        stream.Close();
    }

    private static System.Windows.Media.PixelFormat ConvertBmpPixelFormat(System.Drawing.Imaging.PixelFormat pixelformat)
    {
        System.Windows.Media.PixelFormat pixelFormats = System.Windows.Media.PixelFormats.Default;

        switch (pixelformat)
        {
            case System.Drawing.Imaging.PixelFormat.Format32bppArgb:
                pixelFormats = PixelFormats.Bgr32;
                break;

            case System.Drawing.Imaging.PixelFormat.Format8bppIndexed:
                pixelFormats = PixelFormats.Gray8;
                break;

            case System.Drawing.Imaging.PixelFormat.Format16bppGrayScale:
                pixelFormats = PixelFormats.Gray16;
                break;
        }

        return pixelFormats;
    }

Answer 2

我纠正了你的一些错误（大多是错误的尺码）。但它仍会在b16bpp.Save()上崩溃，因为GDI+ does not support saving 16bit grayscale images。

Bitmap b16bpp;
private void GenerateDummy16bitImage()
{

    b16bpp = new Bitmap(IMAGE_WIDTH, IMAGE_HEIGHT, System.Drawing.Imaging.PixelFormat.Format16bppGrayScale);

    var rect = new Rectangle(0, 0, IMAGE_WIDTH, IMAGE_HEIGHT);
    var bitmapData = b16bpp.LockBits(rect, ImageLockMode.WriteOnly, b16bpp.PixelFormat);
    // Calculate the number of bytes required and allocate them.
    var numberOfBytes = bitmapData.Stride * IMAGE_HEIGHT;
    var bitmapBytes = new short[IMAGE_WIDTH * IMAGE_HEIGHT];
    // Fill the bitmap bytes with random data.
    var random = new Random();
    for (int x = 0; x < IMAGE_WIDTH; x++)
    {
        for (int y = 0; y < IMAGE_HEIGHT; y++)
        {

            var i = ((y * IMAGE_WIDTH) + x); // 16bpp

            // Generate the next random pixel color value.
            var value = (short)random.Next(5);

            bitmapBytes[i] = value;         // GRAY
        }
    }
    // Copy the randomized bits to the bitmap pointer.
    var ptr = bitmapData.Scan0;
    Marshal.Copy(bitmapBytes, 0, ptr, bitmapBytes.Length);

    // Unlock the bitmap, we're all done.
    b16bpp.UnlockBits(bitmapData);

    b16bpp.Save("random.bmp", ImageFormat.Bmp);
    Debug.WriteLine("saved");
}

我的更改说明：

bitmapData.Stride已经IMAGE_WIDTH * BytesPerPixel，因此您无需乘以2
当您将bitmapBytes声明为short[]时，它必须具有以像素为单位的图像大小而不是以字节为单位
表示您也不需要将i乘以2
因为你有一个灰度图像，它没有蓝色，绿色和红色通道，但只有一个16位灰色通道
Marshal.Copy取“数组单位”的长度而不是字节

总而言之，您尝试将数组8次复制到位图中。

生成16位灰度BitmapData并保存到文件

2 个答案: