Question

I am trying to use IM4J (a Java wrapper for ImageMagick) to create thumbnails of JPEGs and it is my first experience (ever) with both libraries. Please note that this is a hard requirement handed to me by my tech lead (so please don’t suggest to use anything other than an IM4J/ImageMagick) solution – my hands are tied on the technology choice here!

I am getting a FileNotFoundException on the and convert command which tells me I don’t have one of these libraries (or both) setup correctly.

On my computer, here is my directory structure:

C:/
    myApp/
        images/             --> where all of my JPEGs are
        thumbnails/         --> where I want ImageMagick to send the converted thumbnails to
        imageMagickHome/    --> Where I downloaded the DLL to
            ImageMagick-6.7.6-1-Q16-windows-dll.exe
    ...
    

In my Java project, I make sure that the IM4J JAR (im4java-1.2.0.jar) is on the classpath at runtime. Although I am required to use the 1.2.0 version of IM4J, I have the liberty to use any version of ImageMagick that I want. I simply chose this version because it seemed like the most current/stable version for my Windows 7 (32-bit) machine. If I should use a different version, please send me a link to it from the ImageMagick downloads page in your answer!

As for ImageMagick, I just downloaded that EXE from here and placed it in the folder mentioned above – I didn’t do any installation, wizard, MSI, environment variable configuration, etc.

Then, in my Java code:

// In my driver...
File currentFile = new File("C:/myApp/images/test.jpg"); --> exists and is sitting at this location
File thumbFile = new File("C:/myApp/thumbnails/test-thumb.jpg"); --> doesnt exist yet! (destination file)
Thumbnailer myThumbnailer = new Thumbnailer();
myThumbnailer.generateThumbnail(currentFile, thumbFile);

// Then the Thumbnailer:
public class Thumbnailer
{
    // ... omitted for brevity
    
    public void generateThumbnail(File originalFile, File thumbnailFile)
    {
        // Reads appConfig.xml from classpath, validates it against a schema,
        // and reads the contents of an element called <imPath> into this
        // method's return value. See below
        String imPath = getIMPathFromAppConfigFile();
    
        org.im4java.core.IMOperation op = new Operation();
        op.colorspace(this.colorSpace);
        op.addImage(originalFile.getAbsolutePath());
        op.flatten();
        op.addImage(thumbnailFile.getAbsolutePath());
        
        ConvertCmd cmd = new ConvertCmd();
        
        cmd.setSearchPath(imPath);
        
        // This next line is what throws the FileNotFoundException
        cmd.run(op);
    }
}

The section of my appConfig.xml file that contains the imPath:

<imPath>C:/myApp/imageMagickHome</imPath>

Please note – if this appConfig.xml is not well-formed, our schema validator will catch it. Since we are not getting schema validation errors, we can rule this out as a culprit. However, notice my file path delimiters; they are all forward slashes. I did this because I was told that, on Windows systems, the forward slash is treated the same as a *nix backslash, in reference to file paths. Believe it or not, we are developing on Windows
machines, but deploying to linux servers, so this was my solution (again, not my call!).

IM4J even acknowledges that Windows users can have trouble sometimes and explains in this article that Windows developers might have to set an IM4JAVA_TOOLPATH env var to get this library to work. I tried this suggestion, created a new System-wide environmental variable of the same name and set its value to C:\myApp\imageMagickHome. Still no difference. But notice here I am using backslashes. This is because this env var is local to my machine, whereas the appConfig.xml is a config descriptor that gets deployed to the linux servers.

From what I can tell, the culprit is probably one (or more) of the following:

• I didn’t "install" the ImageMagick EXE correctly and should have used an installer/MSI; or I need to add some other environmental variables for ImageMagick (not IM4J) itself
• Perhaps I still don’t have IM4J configured correctly and need to add more environmental variables
• Could be the Windows/*nix "/" vs. "" issue from my appConfig.xml file as mentioned above

I’m also perplexed as to why I’m getting a FileNotFoundException on a file named "convert":

java.io.FileNotFoundException: convert

I assume this is a batch/shell file living somewhere inside the IM4J jar (since the only thing I downloaded for ImageMagick was the EXE). However, if I extract the IM4J jar I only see classes inside of it. I see "script generator" classes, so I assume these kick off before my cmd.run(op) call and create the convert file, and maybe that’s what I’m missing (perhaps I need to manually kick off one of these generators, like CmdScriptGenerator prior to executing my Thumbnailer methods. . Or, maybe my download is incomplete.

Either way, I’m just not versed enough with either library to know where to start.

Thanks for any help with this.

Answer 1

Run the ‘ImageMagick-6.7.6-1-Q16-windows-dll.exe’ installer first to install the imagemagick libraries. Then make sure your environment path includes the location of the installed binaries (‘convert.exe’, ‘mogrify.exe’, etc)