The keywords framewidth and frameheight in the button definition in CONFIG.js can be used to define a custom frame size. Example for 'buienradar':
buttons.buienradar = { key: 'buienradar', width:12, isimage:true, refresh:60000, image: 'http://api.buienradar.nl/image/1.0/RadarMapNL?w=256&h=256', url:'https://gadgets.buienradar.nl/gadget/zoommap/?lat=52.06022&lng=4.39288&overname=2&zoom=13&naam=2496hx&size=5&voor=1', framewidth:540, frameheight: 520}
See feature request: https://www.domoticz.com/forum/viewtopic.php?f=67&t=16526&p=197745#p197741
The keywords framewidth and frameheight in the button definition in CONFIG.js can be used to define a custom frame size. Example for 'buienradar':
buttons.buienradar = { key: 'buienradar', width:12, isimage:true, refresh:60000, image: 'http://api.buienradar.nl/image/1.0/RadarMapNL?w=256&h=256', url:'https://gadgets.buienradar.nl/gadget/zoommap/?lat=52.06022&lng=4.39288&overname=2&zoom=13&naam=2496hx&size=5&voor=1', framewidth:540, frameheight: 520}