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CMYK files saved as JPEG are displayd with inverted colors on Mac OS X

Mattias Malm
#1 Posted : Tuesday, April 20, 2010 4:38:14 PM(UTC)
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When saving a CMYK file as JPEG, the file looks great in Windows, but on Mac OS X it looks inverted. A CMYK file saved as JPEG from Photoshop looks great on both platforms, so there is obviously a difference in how GraphicsMill and Photoshop saves CMYK JPEG files. Do you have any suggestions on how to make CMYK JPEG files saved from GraphicsMill work on both Windows and Mac OS X?

You can use Apple Safari on Windows to see the how the CMYK JPEG files look in Mac OS X (see attachment).

Here is a simple example:

CmykJpg.aspx
Code:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="CmykJpg.aspx.cs" Inherits="Tester_CmykJpg" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">

        <asp:FileUpload ID="Image" runat="server" />
        <asp:Button runat="server" OnClick="ConvertToCmyk" Text="Konvertera till CMYK" /><br />
        
        <img src="/Temp/UploadedImage.jpg" />
        <img src="/Temp/ConvertedCmykImage.jpg" />

        <asp:Literal ID="Debug" runat="server" />
        
    </form>
</body>
</html>


CmykJpg.aspx.cs
Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Aurigma.GraphicsMill;

public partial class Tester_CmykJpg : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Debug.Text = "";
    }
    protected void ConvertToCmyk(object sender, EventArgs e)
    {
        // Save uploaded image
        if (Image.PostedFile.ContentLength > 0 && System.IO.Path.GetExtension(Image.PostedFile.FileName).ToLower() == ".jpg")
        {
            Image.PostedFile.SaveAs(Server.MapPath("/Temp/UploadedImage.jpg"));
        }

        // Convert image to CMYK
        if (System.IO.File.Exists(Server.MapPath("/Temp/UploadedImage.jpg")))
        {
            Bitmap gmImage = new Bitmap(Server.MapPath("/Temp/UploadedImage.jpg"));
            gmImage.ColorManagement.ConvertToContinuous(ColorSpace.Cmyk, false, false);
            gmImage.Save(Server.MapPath("/Temp/ConvertedCmykImage.jpg"));
            Response.Redirect("CmykJpg.aspx?" + DateTime.Now.Ticks.ToString());
        }
        else
        {
            Debug.Text = "No uploaded image.";
        }
    }
}


Best Regards
Mattias Malm
Mattias Malm attached the following image(s):
SafariDump.jpg
Tamila
#2 Posted : Wednesday, April 21, 2010 11:52:32 PM(UTC)
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Hello Mattias,

Thank you for the code snippets. We reproduced this problem locally. Our developers investigated the issue and found that it is a known issue of WebKit (used in Safari) on Mac. It seems that WebKit cannot work with CMYK jpeg, if it was created by any application other than Photoshop.
If you try to open your application in Firefox on Mac, you will see that it works properly.

Anyway we will contact Apple about this problem.
Aurigma Support Team

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sosouth
#3 Posted : Thursday, August 12, 2010 7:46:24 AM(UTC)
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I've had this same problem. We use some automated scripts for editing, thought it was us. Images look fine and then all of a sudden I see the inverted b/w image? Seems to be this issue with the Mac system. We are running 10.5.8 pre-Intel machines. Craziest thing the files look fine when dropped on a Firefox window or emailed to other machines. I thought the days of Mac incompatibilities were over.
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