Most of your image size and placement settings can be adjusted with just your mouse using the image border scaling options or by dragging-and-dropping the image's placement.
You can also manually set the image size and location under the "Size & Position" tab located in the right toolbar when selecting the image.
**The term "image field" referenced through this article refers the image container and it's associated height and width and not the original uploaded image itself or that image's associated height or width
Showit provides 2 primary ways to define how an image may respond inside the image field through the "Fill" and "Contain" options. Under the "Image" tab, with an image selected, in the right toolbar you will see a Size option with a drop-down menu.
Image Setting - Fill
The 'Fill' option will force the image to fill all the way to the set height and width dimensions of the image field. This may result in some cropping of the image if the image area and the original image itself are not in equal ratio.
Depending on the horizontal or vertical orientation if the image field, the 'Position' setting will allow you to set how the image is positioned inside the image field.
Image Setting - Contain
The 'Contain' setting will preserve the original image's dimensions inside the image field.
With the image field being set to "Contain", this will allow you to adjust the height and width of the image area without altering the original image's dimensions. The original image will scale with whichever edge is shortest relative to the image.
Image Settings -Background
For a Background Image, it is important to remember that the editor is 1200 pixels wide, while most computer screens are much wider. A Background Image is responsive to the width of any given browser and will stretch relative to the width of the screen. The height of the Canvas containing the Background Image, however, will remain the same height (unless you have set your Canvas to "Window Height" in the "Canvas" tab on the right).
Even if it appears that the Image fits well in the Showit app, anticipate some image changes with how the image may be viewed on different screen or browser sizes. If you find the image is cropping to much from the top or bottom edge on larger screens, increasing the height of the Canvas can be the solution as it will allow a higher responsive ratio for the image dimensions.
Here's a great article on adjusting canvas height.