如何在 ColdFusion (Java) 中在 CMYK 和 RGB 之间转换图

问题描述

我需要将图像从 CMYK 转换为 RGB - 不一定要再转换回来，但是嘿，如果可以的话...

I have a need to convert images from CMYK to RGB - not necessarily back again, but hey, if it can be done...

随着 ColdFusion 8 的发布，我们获得了 CFImage 标签，但它没有'不支持这种转换；Image.cfc 或 Alagad 的图像组件.

With the release of ColdFusion 8, we got the CFImage tag, but it doesn't support this conversion; and nor does Image.cfc, or Alagad's Image Component.

但是，在 Java 中应该是可能的；我们可以通过 CF 加以利用.例如，以下是创建 Java 线程来休眠进程的方法:

However, it should be possible in Java; which we can leverage through CF. For example, here's how you might create a Java thread to sleep a process:

<cfset jthread = createObject("java", "java.lang.Thread")/>
<cfset jthread.sleep(5000)/>

我猜想可以使用类似的方法来利用 java 进行这种图像转换，但不是 Java 开发人员，我不知道从哪里开始.有人可以帮忙吗?

I would guess a similar method could be used to leverage java to do this image conversion, but not being a Java developer, I don't have a clue where to start. Can anyone lend a hand here?

推荐答案

我使用 Java ImageIO 库 (https://jai-imageio.dev.java.net).它们并不完美，但可以很简单并完成工作.至于从 CMYK 转换为 RGB，这是我能想到的最好的.

I use the Java ImageIO libraries (https://jai-imageio.dev.java.net). They aren't perfect, but can be simple and get the job done. As far as converting from CMYK to RGB, here is the best I have been able to come up with.

为您的平台下载并安装 ImageIO JAR 和本机库.本机库是必不可少的.没有它们，ImageIO JAR 文件将无法检测 CMYK 图像.最初，我的印象是本机库会提高性能，但不需要任何功能.我错了.

Download and install the ImageIO JARs and native libraries for your platform. The native libraries are essential. Without them the ImageIO JAR files will not be able to detect the CMYK images. Originally, I was under the impression that the native libraries would improve performance but was not required for any functionality. I was wrong.

我注意到的另一件事是，转换后的 RGB 图像有时比 CMYK 图像轻得多.如果有人知道如何解决这个问题，我将不胜感激.

The only other thing that I noticed is that the converted RGB images are sometimes much lighter than the CMYK images. If anyone knows how to solve that problem, I would be appreciative.

以下是将 CMYK 图像转换为任何支持格式的 RGB 图像的一些代码.

Below is some code to convert a CMYK image into an RGB image of any supported format.

谢谢你，
兰迪·施泰格鲍尔

Thank you,
Randy Stegbauer

package cmyk;

import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorConvertOp;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.apache.commons.lang.StringUtils;

public class Main
{

    /**
     * Creates new RGB images from all the CMYK images passed
     * in on the command line.
     * The new filename generated is, for example "GIF_original_filename.gif".
     *
     */
    public static void main(String[] args)
    {
        for (int ii = 0; ii < args.length; ii++)
        {
            String filename = args[ii];
            boolean cmyk = isCMYK(filename);
            System.out.println(cmyk + ": " + filename);
            if (cmyk)
            {
                try
                {
                    String rgbFile = cmyk2rgb(filename);
                    System.out.println(isCMYK(rgbFile) + ": " + rgbFile);
                }
                catch (IOException e)
                {
                    System.out.println(e.getMessage());
                }
            }
        }
    }

    /**
     * If 'filename' is a CMYK file, then convert the image into RGB,
     * store it into a JPEG file, and return the new filename.
     *
     * @param filename
     */
    private static String cmyk2rgb(String filename) throws IOException
    {
        // Change this format into any ImageIO supported format.
        String format = "gif";
        File imageFile = new File(filename);
        String rgbFilename = filename;
        BufferedImage image = ImageIO.read(imageFile);
        if (image != null)
        {
            int colorSpaceType = image.getColorModel().getColorSpace().getType();
            if (colorSpaceType == ColorSpace.TYPE_CMYK)
            {
                BufferedImage rgbImage =
                    new BufferedImage(
                        image.getWidth(), image.getHeight(), BufferedImage.TYPE_3BYTE_BGR);
                ColorConvertOp op = new ColorConvertOp(null);
                op.filter(image, rgbImage);

                rgbFilename = changeExtension(imageFile.getName(), format);
                rgbFilename = new File(imageFile.getParent(), format + "_" + rgbFilename).getPath();
                ImageIO.write(rgbImage, format, new File(rgbFilename));
            }
        }
        return rgbFilename;
    }

    /**
     * Change the extension of 'filename' to 'newExtension'.
     *
     * @param filename
     * @param newExtension
     * @return filename with new extension
     */
    private static String changeExtension(String filename, String newExtension)
    {
        String result = filename;
        if (filename != null && newExtension != null && newExtension.length() != 0);
        {
            int dot = filename.lastIndexOf('.');
            if (dot != -1)
            {
                result = filename.substring(0, dot) + '.' + newExtension;
            }
        }
        return result;
    }

    private static boolean isCMYK(String filename)
    {
        boolean result = false;
        BufferedImage img = null;
        try
        {
            img = ImageIO.read(new File(filename));
        }
        catch (IOException e)
        {
            System.out.println(e.getMessage() + ": " + filename);
        }
        if (img != null)
        {
            int colorSpaceType = img.getColorModel().getColorSpace().getType();
            result = colorSpaceType == ColorSpace.TYPE_CMYK;
        }

        return result;
    }
}

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