如何访问 1、2、4 bpp 图像的像素？

Question

如果给定图像具有 8、24 或 32bpp，我有一个工作代码可以访问确定的像素值。这是代码：

使用BitmapSource：

// Get width and height of bitmap
Width = _source.PixelWidth;
Height = _source.PixelHeight;

// Get total locked pixels count
int pixelCount = Width * Height;

// Get source bitmap pixel format size
Depth = _source.Format.BitsPerPixel;

// Create byte array to copy pixel values
int step = Depth / 8;
Pixels = new byte[pixelCount * step];
_iptr = _data.BackBuffer;

// Copy data from pointer to array
Marshal.Copy(_iptr, Pixels, 0, Pixels.Length);

int count = Depth / 8;

if (count == 0)
    count = 1;

//Get start index of the specified pixel
int i = ((y * Width) + x) * count;

if (i > Pixels.Length - count)
    throw new IndexOutOfRangeException();

if (Depth == 32) //For 32 bpp get Red, Green, Blue and Alpha
{
    byte b = Pixels[i];
    byte g = Pixels[i + 1];
    byte r = Pixels[i + 2];
    byte a = Pixels[i + 3]; // a
    clr = Color.FromArgb(a, r, g, b);
}
else if (Depth == 24) //For 24 bpp get Red, Green and Blue
{
    byte b = Pixels[i];
    byte g = Pixels[i + 1];
    byte r = Pixels[i + 2];
    clr = Color.FromRgb(r, g, b);
}
else if (Depth == 8) //For 8 bpp get color value (Red, Green and Blue values are the same)
{
    byte c = Pixels[i];
    clr = Color.FromRgb(c, c, c);
}

并设置像素值：

if (Depth == 32) //For 32 bpp set Red, Green, Blue and Alpha
{
    Pixels[i] = color.B;
    Pixels[i + 1] = color.G;
    Pixels[i + 2] = color.R;
    Pixels[i + 3] = color.A;
}
else if (Depth == 24) //For 24 bpp set Red, Green and Blue
{
    Pixels[i] = color.B;
    Pixels[i + 1] = color.G;
    Pixels[i + 2] = color.R;
}
else if (Depth == 8) //For 8 bpp set color value (Red, Green and Blue values are the same)
{
    Pixels[i] = color.B;
}

那么，我如何访问（获取、设置）1,2 或 4bpp 像素值？

Answer 1

我目前正在将图像转换为其他一些Format，然后再尝试读取像素值。这解决了我的问题。