Increasing Print Quality for images

Question

Hi.

I'm writing a program that needs to print off high resolution .tiff images. The problem I'm having is that I can't print the .tiff's in good quality. Due to the large size of the .tiff (8700x7200 for instance) It will not fit on any standard sized sheet. I tried increasing the DPI but that didn't seem to have any effect. The only way i can get the .tiff to fit the page is to scale it down. but then the image has horrendous quality. (I scale it down to fit on a 11x17, but that only has an indicated resolution of 1100x1700). i tried changing the resolutions ettings on the printer, tried manually and programatically setting the printer quality/resolution but to no success. Basically I want to be able to fit more pixels of the .tiff onto the 11x17 page so I don't have to scale as much. I thought increasing the print dpi would increase the amount of pixels on an 11x17 inches, but it had no effect I could see. Maybe I'm doing something wrong. Any help would be greatly appreciated. thanks.

The code below is what I'm attempting to do right now when pd.Print() is invoked.

    private void pd_PrintPage(object sender, PrintPageEventArgs ev)
    {
        //float x = ev.MarginBounds.Left;
        //float y = ev.MarginBounds.Top;
        try
        {
            //ResizeImage(@"H:\21RR-G0K-30140-0220-0002.tiff", @"H:\21RR-G0K-30140-0220-0002-new.tiff", 500, 900, false);
            Image tempImage = Image.FromFile(@"H:\21RR-G0K-30140-0220-0002.tiff");
            Bitmap bMap = new Bitmap(tempImage);
            bMap.SetResolution(1200, 1200);
            string l = "";
            tempImage = bMap;
            /*if (tempImage.Width > tempImage.Height)  //if poster is longer then it is tall, rotate the image. Done to match standard printing aspect ratios
            {
                Bitmap tempBitmap = new Bitmap(tempImage); //Need to convert to Bitmap type to do rotation
                RotateBicubic rotationFilter = new RotateBicubic(90, true);
                tempImage = rotationFilter.Apply(tempBitmap);
            }*/
            float ImageAspectRatio = (float)tempImage.Height / (float)tempImage.Width;  
            float PageSizeAspectRatio = (float)_pSize.Height / (float)_pSize.Width; //_pSize is the selected printing sheet size
            if (ImageAspectRatio < 1 && PageSizeAspectRatio > 1) //Need to rotate Image. Can't attempt to rotate tempImage due to size. Scale then rotate.
            {
                double x_scale = (double)_pSize.Width / (double)tempImage.Height;
                double y_scale = (double)_pSize.Height / (double)tempImage.Width;
                int percent = 0;
                if (y_scale < x_scale)
                {
                    percent = Convert.ToInt32(y_scale * 100);
                }
                else
                {
                    percent = Convert.ToInt32(x_scale * 100);
                }
                Image myImage = ImageManipulation.ScaleByPercent(tempImage, percent); //I know this line is the problem, but I can't fit the image on the page without massive scaling due to the page reolution restraints
                Bitmap tempMap = new Bitmap(myImage);
                tempMap.SetResolution(1200, 1200);
                RotateBicubic rotateBC = new RotateBicubic(90);
                Image finalImage = rotateBC.Apply(tempMap); //rotate the image 90 degrees using bicubic interpolation. This isn't what's killing the quality as the quality is no better with this disabled
                ev.Graphics.DrawImage(finalImage, 0, 0);
            }
            else if (ImageAspectRatio >= 1 && PageSizeAspectRatio >= 1) //No Need for rotation 
            {
                double x_scale = (double)_pSize.Width / (double)tempImage.Width;
                double y_scale = (double)_pSize.Height / (double)tempImage.Height;
                int percent = 0;
                if (y_scale < x_scale)
                {
                    percent = Convert.ToInt32(y_scale * 100);
                }
                else
                {
                    percent = Convert.ToInt32(x_scale * 100);
                }

                Image myImage = ImageManipulation.ScaleByPercent(tempImage, percent);
                ev.Graphics.DrawImage(myImage, 0, 0);

            }

            else
            {

            }              
        }
        catch(Exception ex)
        {
            string breakingpoint = "";
        }
    }

Answer 1

It appears that the problem is in the scaling routine. Maybe you should look into some third-party libraries that include high-quality scaling algorithms.

Answer 2

The term you are looking for is "resampling."

It's also probably best to scale the image using the device coordinate system or the GDI+ HIENGLISH units (I believe that's what's used on a printing device context.)

Using the DrawImage command the best you're going to get from GDI+ is the HighQualityBicubic Resampling.

    Private Sub pd_PrintPage(ByVal sender As System.Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles pd.PrintPage

        Dim img As Image = Image.FromFile("SAMPLE.TIF")

        Dim imageWidth As Integer = CInt((img.Width / img.HorizontalResolution) * 100)
        Dim imageHeight As Integer = CInt((img.Height / img.VerticalResolution) * 100)

        If imageWidth > e.PageBounds.Width Then
            Dim ratio As Double = imageWidth / imageHeight
            imageWidth = e.PageBounds.Width
            If ratio < 1 Then
                imageHeight = CInt(imageWidth * ratio)
            Else
                imageHeight = CInt(imageWidth / ratio)
            End If
        End If

        If imageHeight > e.PageBounds.Height Then
            Dim ratio As Double = imageHeight / imageWidth
            imageHeight = e.PageBounds.Height
            If ratio < 1 Then
                imageWidth = CInt(imageHeight * ratio)
            Else
                imageWidth = CInt(imageHeight / ratio)
            End If
        End If

        e.Graphics.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
        e.Graphics.DrawImage(img, 0, 0, imageWidth, imageHeight)

    End Sub