Graphics Class isn't drawing to image

Development
1

Hey there! I’m relatively new to Juce and am having troubles with my graphics class. The graphics for the paint() function works fine without troubles however I want to save an image based on some info I gather from the window. As such I created an Image and then a Graphics using that image: The code is as follows:

void saveGraphAsImage()
{
//check that window size is greater than 0
if (getWidth() > 0 && getHeight() > 0)
{
// Create Image Data
juce::Image image(juce::Image::RGB, getWidth(), getHeight(), false);

    // Create graphics to draw data to image
    juce::Graphics g(image);
    g.setOpacity(1.0f);
    g.fillAll(juce::Colours::green);
    g.setColour(juce::Colours::yellow);
    g.fillEllipse(200, 200, 200, 200);

    // save image
    juce::File outputFile = File::getCurrentWorkingDirectory().getChildFile("spectrum.png");
    juce::PNGImageFormat pngFormat;
    if (auto outputStream = outputFile.createOutputStream())
        pngFormat.writeImageToStream(image, *outputStream);
}

}
I’ve tried to solve this after looking through all the documentation however no matter what I do the graphics class doesn’t do anything. I can directly edit the image and save that (for instance a for loop that draws a line or box works fine) however that defeats the point of the Graphics class altogether and I have more complex drawing needs. Any idea why my graphics is just not drawing on my image?

2

Try adding some curly braces around the Graphics instance like so:

juce::Image image(juce::Image::RGB, getWidth(), getHeight(), false);

{
    // Create graphics to draw data to image
    juce::Graphics g(image);
    g.setOpacity(1.0f);
    g.fillAll(juce::Colours::green);
    g.setColour(juce::Colours::yellow);
    g.fillEllipse(200, 200, 200, 200);
}

// save image
auto outputFile = File::getCurrentWorkingDirectory().getChildFile("spectrum.png");

On some platforms, the Graphics object will not update the image until its destructor runs, i.e. it goes out-of-scope.

2 Likes
3

Thank you! This fixed the problem.