[2005] Image Mode

[clarkgriswald]

I want to allow the user to select a file from the file system to use on a web page, but images that are CMYK as opposed to RGB, will not display in web browsers and I wanted to know if there was any type of image analyzing I could do when the user selects the file to determine if the image is a "valid" web image?

[Ken B]

Look at the picture PixelFormat. Lookup PixelFormat enumeration in help for a list of image types.

 
  Public Structure ImageInformation

    Dim Extension As String
    Dim FileExist As Boolean
    Dim FullFileName As String         'Full path and file name of image.
    Dim HorizontalResolution As Single 'Horizontal resolution, in pixels per inch.
    Dim ImageSize As pdfImageSize
    Dim Length As Double               'Length of a file in bytes.
    Dim Name As String                 'Image file name without path.
    Dim PDFName As String              'Internal name of image loaded into the pdf document.
    Dim PixelFormat As String          'The pixel format defines the number of bits of memory associated with one pixel of data. The format also defines the order of the color components within a single pixel of data.
    Dim VerticalResolution As Single   'Vertical resolution, in pixels per inch.
    Dim ValidImage As Boolean

  End Structure

Public Function GetImageFileInfo(ByVal ImageFileName As String) As ImageInformation

    Dim tmpInfo As New ImageInformation

    If Not System.IO.File.Exists(ImageFileName) Then
      tmpInfo.ValidImage = False
      Return tmpInfo
    End If

    Dim ioFile As New System.IO.FileInfo(ImageFileName)

    Dim bit As New Bitmap(ImageFileName)
    Try
      tmpInfo.Extension = ioFile.Extension
      tmpInfo.FileExist = True
      tmpInfo.FullFileName = ImageFileName
      tmpInfo.HorizontalResolution = bit.HorizontalResolution
      tmpInfo.Length = FileLen(ImageFileName)
      tmpInfo.PixelFormat = bit.PixelFormat.ToString
      tmpInfo.Name = ioFile.Name
      tmpInfo.ImageSize = New pdfImageSize(bit.Width, bit.Height)
      tmpInfo.ValidImage = True
      tmpInfo.VerticalResolution = bit.VerticalResolution

    Catch ex As Exception
      tmpInfo.FullFileName = ImageFileName
      tmpInfo.ValidImage = False

    Finally
      bit.Dispose()

    End Try

    Return tmpInfo

  End Function

[clarkgriswald]

The PixelFormat for my RGB image and CMYK image return the same values, yet the RGB image is supported and the CMYK image is not. Any other suggestions?

[Ken B]

How about converting them to a format you can used?

Try:

  Public Function ReCreateImage(ByVal ImageFileName As String, ByVal NewImageFileName As String, ByVal NewResolution As Single) As Boolean

    If ImageFileName = String.Empty Then
      MessageBox.Show("'Image File Name' is required for ReCreateImage.", "vbPDF Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
      Return False
    End If

    If NewImageFileName = String.Empty Then
      MessageBox.Show("'New Image File Name' is required for ReCreateImage.", "vbPDF Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
      Return False
    End If

    If Not System.IO.File.Exists(ImageFileName) Then Return False

    Dim orginalImage As New Bitmap(ImageFileName)
    Try
      If System.IO.File.Exists(NewImageFileName) Then System.IO.File.Delete(NewImageFileName)
      orginalImage.SetResolution(NewResolution, NewResolution)
      orginalImage.Save(NewImageFileName, System.Drawing.Imaging.ImageFormat.Jpeg)
      orginalImage.Dispose()

    Catch exIO As System.IO.IOException
      MessageBox.Show("IOException in reCreateImage." & Environment.NewLine & Environment.NewLine & exIO.Message, "vbPDF Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
      Return False

    Catch ex As Exception
      MessageBox.Show("Exception in reCreateImage." & Environment.NewLine & Environment.NewLine & ex.Message, "vbPDF Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
      Return False

    Finally
      orginalImage.Dispose()

    End Try

    Return True

  End Function

[clarkgriswald]

Good alternative, it would be nice to let them know that I am creating a new image as opposed to using a new one. Is there any way to determine if the image is supported in HTML?

[bmahler]

GDI does not have a way to determine if the image is CMYK so atm your best option is to convert the images to an acceptable format for the web. If you save the image copy as a jpg, I have found that it retains the CMYK format. I personally change them to RGB PNG images and it works fine.

here is the code I use for easily converting it to an 8bit RGB png

Dim inImage As Bitmap = Image.FromFile("C:\test.jpg")
Dim imgRegion As RectangleF = inImage.GetBounds(System.Drawing.GraphicsUnit.Pixel)
Dim outImage As Bitmap = inImage.Clone(imgRegion, Imaging.PixelFormat.Format24bppRgb)
outImage.Save("C:\text_copy.png", System.Drawing.Imaging.ImageFormat.Png)