Eduardo,
The purple box on your second image is the "Render Region". Here you are saying "only render what is inside this box". It is there to help you make adjustments. It has NOTHING to do with the size of the output image file.
To control that, go the the PhotoView Options. If you select "use SolidWorks View", you will get exactly the size of the SolidWorks window on your screen (with the Feature Manager tree hidden). THAT is the black box on your first image. So you need to resize the SolidWorks window to be exactly what you want in the final render. In other words, adjust the window size to match your render region box.
Now a much better way to control your output image size is the use a Camera View. Set up a new Camera the way you like it, then choose that Camera from the view-port menu. Now do your rendering.
Eduardo,
The purple box on your second image is the "Render Region". Here you are saying "only render what is inside this box". It is there to help you make adjustments. It has NOTHING to do with the size of the output image file.
To control that, go the the PhotoView Options. If you select "use SolidWorks View", you will get exactly the size of the SolidWorks window on your screen (with the Feature Manager tree hidden). THAT is the black box on your first image. So you need to resize the SolidWorks window to be exactly what you want in the final render. In other words, adjust the window size to match your render region box.
Now a much better way to control your output image size is the use a Camera View. Set up a new Camera the way you like it, then choose that Camera from the view-port menu. Now do your rendering.