Sebastian Sebastian - 1 year ago 199 Question

iTextSharp renders image with poor quality in PDF

I'm using iTextSharp to print a PDF document. Everything goes ok until I have to print the company logo in it.

First I noticed that the logo had poor quality, but after testing with several images, I realize that was the iTextSharp rendering it poorly.
The test I did to say this was to print the PDF using my code and then edit the document with Acrobat 8.0 and I drew an image. Then printed the two documents and saw the noticeable difference.
My question is that if anyone know if this can be due to a scaling problem where I'm failing to tell iTextSharp how it must render the image or is an iTextSharp limitation.

The code to render the image is the following:

Dim para As Paragraph = New Paragraph
para.Alignment = Image.RIGHT_ALIGN

Dim imageFile As String = String.Format("{0}{1}", GetAppSetting("UploadDirectory"), myCompany.LogoUrl)

Dim thisImage As Image = Image.GetInstance(imageFile)
thisImage.Alignment = Image.LEFT_ALIGN


The printed images are the following:
alt text

Image printed directly with iTextSharp

alt text

Image edited and printed with Acrobat 8

These logo images are loaded from an Upload page where the user uploades whatever the logo image he wants, and I was scaling that image using the following code:

Dim graph As System.Drawing.Graphics = System.Drawing.Graphics.FromImage(newImage)

graph.CompositingMode = Drawing.Drawing2D.CompositingMode.SourceOver
graph.CompositingQuality = Drawing.Drawing2D.CompositingQuality.HighQuality
graph.InterpolationMode = Drawing.Drawing2D.InterpolationMode.Bicubic
graph.SmoothingMode = Drawing.Drawing2D.SmoothingMode.HighQuality
graph.PixelOffsetMode = Drawing.Drawing2D.PixelOffsetMode.HighQuality

graph.DrawImage(newImage, 0, 0, newWidth, newHeight)

graph = Nothing

This was causing to lose info from the original image, so when printed in the pdf, that lose of info was very noticeable because, somehow, iTextSharp was drawing bigger than it was, no matter the scaling I put in there.
So I tried to store the image as it was originally, preventing the user to not upload images bigger than 200K and resizing the image so I could mantain the aspect ratio, and using that resizing with the iTextSharp Image object before it was printed.
This solved my problem of the image being printed with poor quality for these bigger images but caused the pdf document to have a page break or just not fit in the page, weird thing because the picture looks good in size but it behaves like it was bigger.
This is a screen capture of the new image:
alt text


When inspecting the iTextSharp Image that is sent to be printed, it shows no changes after the scaling using ScaleAbsolute, that's why the page breaks. But is shown correctly, like the image was successfully scaled, but the background "paper" wasn't.
The code used so far is the following:

Dim imageFile As String = String.Format("{0}{1}", GetAppSetting("UploadDirectory"), myCompany.LogoUrl)

Dim thisImage As Image = Image.GetInstance(imageFile)
thisImage.Alignment = Image.LEFT_ALIGN

Dim newWidth As Integer = myCompany.LogoWidth
Dim newHeight As Integer = myCompany.LogoHeight
ResizeImageToMaxValues(newWidth, newHeight)
thisImage.ScaleAbsolute(newWidth, newHeight)



The method ResizeImage() do the resizing of the width and height respecting the aspect ratio and keeping in a max width and a max height limits.

Please let me know if I need to provide more info. Thanks

Answer Source

I also have good experience with iTextSharp rendering very sharp and clear images. I tried both adding the image directly to the document and adding it to a paragraph first. Both give very clear results.

Dim document As Document = New Document(pSize, 20, 20, 20, 20)
PdfWriter.GetInstance(document, New FileStream(myPath & "Test.pdf", FileMode.Create))

Dim png As Image = Image.GetInstance(myPath & "myImageFile.png")

Dim pgr As New Paragraph

I normally use .png images, but I have had the same success with jpeg, gif, etc.

Are you certain that when you retrieve the image in iTextSharp it is the exact same image that you retrieve when you are in Acrobat? I ask because it is unclear what exaclty is happening in your code:

Dim imageFile As String=String.Format(.....


Also, to make sure that the image is displaying at the size you are expecting, save your images at 72dpi. 72 dpi is what iTextSharp uses for everything (images, margins, etc..). That way, a 100px x 100px image will show up as 100x100 on your pdf document. You won't have to worry about scaling or re-sizing then. Any time that you scale an image (up or down) you run the risk of introducing aliasing artifacts (blurriness).

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