Color changed when creating a PDF from an image

[louis]

Hi,

I display a pdf file with text in red color. Then, I create a new pdf file from the image which is displayed, with PdfAddImageFromGdPictureImage and PdfDrawImage. The red color in the new file is dark.
Is there a property to use when creating the pdf ?

Louis

[Loïc]

Hi,

Could you provide files + code snippet to illustrate your issue ?

Kind regards,

Loïc

[louis]

Hi,

The pdf files cannot be uploaded, so I send them to the support.
This is the code :

Code: Select all

Private Sub TestGdDarkRedColor()
    Dim w!, h!
    Dim ImageF&
    Dim iFont&, status&
    Dim path$
   
    ' display RedColor.Pdf : no problem
    GDV_File.BackColor = vbWhite
    GDV_File.PdfDpiRendering = 110
    GDV_File.Clear
    GDV_File.CloseImage
    GDV_File.SilentMode = True
    path = "RedColor.pdf"
    status = GDV_File.DisplayFromPdfFile(path)
    h = GDV_File.GetHeightMM / 10
    w = GDV_File.GetWidthMM / 10
   
    GDV_File.SilentMode = False
    GDV_File.SetZoomFitControl
    GDV_File.ContinuousViewMode = False
    GDV_File.MouseWheelMode = 0
   
    ' generate RedColorGd.pdf : red color becomes dark
    path = "RedColorGd.pdf"
    GDI_File.CloseNativeImage
    If GDI_File.PdfNewPdf(path, "", "", "", "") Then
        GDI_File.PdfSetMeasurementUnits (2) ' cm
        GDI_File.PdfSetPageDimensions MWidth / 10, MHeight / 10
        iFont = GDI_File.PdfAddFont("Arial", True)
       
        ImageF = GDI_File.PdfAddImageFromGdPictureImage(GDV_File.GetNativeImage)
       
        GDI_File.PdfNewPage
        Call GDI_File.PdfDrawImage(ImageF, 0, 0, w, h)
        GDI_File.PdfEndPage
       
        GDV_File.Clear
        GDV_File.CloseImage
        GDI_File.PdfSavePdf
     End If
End Sub



Louis

[Loïc]

Hi,

I think you can get pretty similar result with

Code: Select all

GDV_File.PdfDpiRendering = 72

and

Code: Select all

GDI_File.PdfSetJpegQuality (100)

Kind regards,

Loïc

[louis]

Hi,

There is no change with PdfDpiRendering = 72 and PdfSetJpegQuality (100).

That's strange because the operation I'm making is basic. Did you get the same problem ?

Louis

[Loïc]

Hi Louis,

Keep in mind that you are converting PDF with vector objects to a PDF including only image due to the rasterization process.
Therefore, you will more or less different result depending on the viewer you are using.

Kind regards,

Loïc

[louis]

Hi again,

I understand what you mean about the conversion but I think that there may be a little problem, or maybe some other properties or methods to use. It's strange that, if we add red text on a white page, then we create the pdf, we display it and we save it again, the simple red color is changed. With Adobe Acrobat for example, there is no change.

Sorry to be insistent ! We would like to develop a perfect tool !

Louis

[Loïc]

Louis your comparison is wrong:

You are comparing what Adobe shows you at screen from a vector document, to this same document rasterized to an image format with dataloss compression (JPEG)


If you want to make a comparison between what Adobe done, please have a look on the attached image. it is your document opened by acrobat and saved as JPEG. As you can see the result is exactly the same as GdPicture.

I done the test with 200 dpi rendering, maybe you should try this value.