Okay so I finished rendering my image and was playing around with the image in the compositor. After I saved the file and quit. But later when I open the file and go to the compositor the image on the render layer node is empty. So my question is is there a way to save the render image and when you close blender and open it back the image is still there?
For 2.49b or earlier:
Not using Render Layers, no. The layer renderings are held in buffers that are cleared when the file is closed or Blender quits, and are not saved.
I believe you can save the Render Layer output as an EXR file using an Output>File Output node, but you have to input that with a different node (Input>Image), and this isn’t the same as the Render Layer itself.
Thanks chipmasque for your answer. I thought I might have re render the image again. The image that was gone took me about five hours for it to be finish and I didn’t want to do it again.
Just save the image! After rendering, hit F3 to open a save dialog in a window. I suggest the PNG image format, it’s lossless but very economical in file size.
This doesn’t save the Render Layers, though, just whatever is piped to an Output>Composite node, or a File Output node, if you’re using Do Composite.
For WIPs that use Render Layers, you can render each layer separately using the “Re-render this layer” button at the far right of the Render Layer node controls strip. This can save having to re-render the entire scene. But for a full composite, you’ll need to re-render them all after opening the file anew.
EDIT: Actually, come to think of it, you could try using the “Save buffers” option – it’s a button in the Scene>Output panel. This saves all your Render Layers as temporary .EXR files when you close. I think this is what you’re trying to do, or as close as Blender can get.