Question

我有一个PNG文件，其颜色深度为8位，这由文件属性证明：

是的，当我打开文件

var filePath = "00050-w600.png";
var bitmap = new Bitmap(filePath);
Console.WriteLine(bitmap.PixelFormat);

我得到Format32bppArgb。我还查看了PropertyIdList和PropertyItems属性，但看不到任何明显的内容。

那么我该如何从PNG中提取位深度？

P.S。框架方法似乎都不起作用。 System.Windows.Media.Imaging.BitmapSource可能有效，但仅在WPF和.NET Core 3中有效。对于.NET 4.x和.NET Core 2.x，我需要使用它。

P.P.S。我只需要知道PNG是否为8位，所以我写了一个确定的fire方法来检查是否有人需要-应该在任何框架中工作。

public static bool IsPng8BitColorDepth(string filePath)
{
    const int COLOR_TYPE_BITS_8 = 3;
    const int COLOR_DEPTH_8 = 8;
    int startReadPosition = 24;
    int colorDepthPositionOffset = 0;
    int colorTypePositionOffset = 1;

    try
    {
        using (var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            fs.Position = startReadPosition; 

            byte[] buffer = new byte[2];
            fs.Read(buffer, 0, 2);

            int colorDepthValue = buffer[colorDepthPositionOffset];
            int colorTypeValue = buffer[colorTypePositionOffset];

            return colorDepthValue == COLOR_DEPTH_8 && colorTypeValue == COLOR_TYPE_BITS_8;
        }
    } 
    catch (Exception)
    {
        return false;
    }
}

   Color   Allowed       Interpretation
   Type    Bit Depths

   0       1,2,4,8,16    Each pixel value is a grayscale level.

   2       8,16          Each pixel value is an R,G,B series.

   3       1,2,4,8       Each pixel value is a palette index;
                         a PLTE chunk must appear.

   4       8,16          Each pixel value is a grayscale level,
                         followed by an alpha channel level.

   6       8,16          Each pixel value is an R,G,B series,
                         followed by an alpha channel level.

如何查询PNG的位深度？

0 个答案: