flutter making image with rounded corners and adding bottom text
  use black for gradients and white for text, otherwise some pics are
  lighter in the bottom and your text will not be seen
  we use stack to overlay gradient and text

Container - optional to set height and width
   Cliprrect - for rounder corners
     child: Stack  - child of Cliprrect
        [ // children of stack
          image
          Positioned - for gradient and text
        ]

flutter code - pass a valid pic url to addImage

       Container(
          height: 200, width: 200,       ///////////optional
          margin: EdgeInsets.all(9.0),
          child: ClipRRect(             //////////rounded corners
            borderRadius: BorderRadius.circular(15.0),
            child: Stack(children: [ //////////overlay gradient and text
               addImage(picURL),
               Positioned(bottom: 0, left: 0, right: 0, child: containerWithGradAndText()),               
            ],),//stack, widget children
          ),//cliprrect
        ),//container
      ),//scaffold
     );}//material app, build


//////////////functions to not pollute above

//////////// fill container with image
  Widget addImage(String pic){return Positioned.fill(child: Image.network('$pic', fit: BoxFit.cover));}
  
  //////////////// add bottom black gradient to image
  LinearGradient myGradient() {return LinearGradient( begin: Alignment.topCenter, end: Alignment.bottomCenter, colors: [Colors.black26, Colors.black],);}

  
  /////////////////// add text to image
  Widget addText(String s){return Text('$s',style:TextStyle(color:Colors.white),);}
 
  //////////////////// container with gradient and text
  Widget containerWithGradAndText(){return
    Container(
    padding: EdgeInsets.all(9.0),
    decoration: BoxDecoration(gradient: myGradient()),
    child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [addText('line1'), addText('line2')]));}