如何从 leadtools 将位图转换为光栅图像

Question

I am trying to convert a screenshot from my screen as a bitmap into a rasterimage

public static RasterImage TakeScreenShot()
        {
            // Capture a screenshot of the area of the screen containing the pixel
            using (Bitmap screenshot = new Bitmap(1920, 1080))
            {
                using (Graphics g = Graphics.FromImage(screenshot))
                {
                    g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(1920, 1080));

                    string path = System.IO.Path.Combine(Environment.GetFolderPath(
    Environment.SpecialFolder.MyDoc‌​uments), "bitmap.bmp");

                    screenshot.Save(path);
                    using (RasterCodecs codecs = new RasterCodecs())
                    {
                        RasterImage image = codecs.Load(path, 0, CodecsLoadByteOrder.BgrOrGray, 0, 0);
                        // The RasterImage object now contains the same image data as the Bitmap object
                        return image;
                    }
                }
            }

        }

I am currently getting an error at RasterImage image = codecs.Load(path, 0, CodecsLoadByteOrder.BgrOrGray, 0, 0);"Page not found"

Answer 1

From documentation :

firstPage
1-based index of the first page to load.

lastPage
The 1-based index of the last page to load. Must be greater than or equal to firstPage. You can pass -1 to load from firstPage to the last page in the file.

The page index starts with 1 but you pass 0 . So you could just try this:

RasterImage image = codecs.Load(path, 0, CodecsLoadByteOrder.BgrOrGray, 1, 1);

Answer 2

As Stephan mentioned, if you want to save to a temp path and then reload it you need to pass the correct page number (1 in this instance) or use the overload method that loads the first page:

RasterImage image = codecs.Load(path);

Another option is using the RasterImageConverter to convert the Bitmap to RasterImage in memory instead of saving to a temp file like so:

public static RasterImage TakeScreenShot()
{
    // Capture a screenshot of the area of the screen containing the pixel
    using (Bitmap screenshot = new Bitmap(1920, 1080))
    {
        using (Graphics g = Graphics.FromImage(screenshot))
        {
            g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(1920, 1080));

            RasterImage image = RasterImageConverter.ConvertFromImage(screenshot, ConvertFromImageOptions.None);
            return image;
        }
    }
}

This is in the Leadtools.Drawing assembly and here is the documentation link: ConvertFromImage