Convert JPG with CMYK color space to RGB in .NET

Question

Well, I think the title mostly says it. I want to upload an image that might be in a variety of formats. In general I then want to save it as is. But if it's JPG with a CMYK color space, I want to convert the color space to RGB when I save it. Is there an easy way to do this in VB.NET? (Or a hard way?)

You do realize you will lose quality re-saving a JPG. I am presuming you have a specific need for RGB? — Dreamwalker, Apr 16 '14 at 15:06
Have you seen [onverting CMYK Jpegs to RBG format](http://www.maxostudio.com/Tut_CS_CMYK.cfm)?? seem it does what you need !!! — huMpty duMpty, Apr 16 '14 at 15:07
I have to assume that these answers would be very helpful (although it's asking for the reverse) - http://stackoverflow.com/questions/5237104/c-sharp-convert-rgb-value-to-cmyk-using-an-icc-profile — EkoostikMartin, Apr 16 '14 at 15:09
@Dreamwalker Sure. But my client is addicted to IE8, and IE8 cannot display CMYK JPGs -- you just get the Red X of Death. So a degraded image is better than no image at all. — Jay, Apr 16 '14 at 20:29
@huMptyduMpty I haven't tried it yet, but it looks like what I need. Thanks. — Jay, Apr 16 '14 at 20:39

score 0 · Answer 1 · edited Jul 11 '17 at 09:30

This is a simple recursive CMYK to RGB JPEG converter:

<%@ OutputCache Duration="600" VaryByParam="*" %>
<%@ Page Debug="false" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Import Namespace="System.IO" %>

<script language="VB" runat="server">

' CMYK to RGB image converter v1.0

Dim MyFolder as String = "PHOTO"

Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    response.write ("<!DOCTYPE html><HTML><HEAD><TITLE>CMYK to RGB converter</TITLE><STYLE>HTML {margin:0px}BODY {font-family:Arial,Helvetica,SansSerif;margin:10px}</STYLE></HEAD><BODY><H1>CMYK to RGB converter</H1><H3>v1.0 by TFI</H3><BR>Image folder: <b>"+MyFolder+"</b><BR><BR>")
    Dim dir As String = Server.MapPath(".")
    Dim folders() As String = Directory.GetDirectories(dir)     
    for each folder as String in folders        
        if mid(folder,InStrRev(folder,"\")+1)=MyFolder then
            Dim files() As String = Directory.GetFiles(folder,"*.jpg",SearchOption.AllDirectories)
            if ubound(files)>=0 then
                for each file as String in files
                    Response.write ("Converting "+file)
                    Convert(file)
                    Response.Flush()
                next
            else
                response.write ("No images found.")
            end if
        end if  
    Next
    response.write ("</BODY></HTML>")
End Sub 

Sub Convert(imageName as String)
    Dim imgFullSizeTemp As System.Drawing.Image
    imgFullSizeTemp = System.Drawing.Image.FromFile(imageName)      
    If imgFullSizeTemp Is Nothing Then Response.End()   
    Dim imgFullSize as new Bitmap(imgFullSizeTemp.Width, imgFullSizeTemp.Height, PixelFormat.Format24bppRgb)
    Dim g As Graphics = Graphics.FromImage(imgFullSize)         
    g.DrawImage(imgFullSizeTemp, 0, 0, imgFullSizeTemp.Width, imgFullSizeTemp.Height)   
    g.Dispose()
    imgFullSizeTemp.Dispose()
    response.write (" >>> Converted!<BR><BR>")
    Dim clone as new Bitmap(imgFullSize)
    clone.Save(imageName, ImageFormat.Jpeg)
End Sub

</script>

Convert JPG with CMYK color space to RGB in .NET

1 Answers1