Performance when rendering object(2d)

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C++

I've noticed in my small game that I get very low fps very quickly when multiple objects are on the screen.

The two objects that hogs performance are enemies and shots fired by either the player or the enemy.

After looping through a vector and moving all enemies I loop the vector again and renders each enemy.

void renderEnemy(){
for (int i = 0;i<enemyVector.size();i++){
enemyVector[i].drawEnemy();
}
};

void enemy::drawEnemy(){
const string playerFilename       = "SmallMine.tif";
const int    DROPS_X_FRAME_COUNT = 1;
const int    DROPS_Y_FRAME_COUNT = 1;
VGCImage     player               = VGCDisplay::openImage(
    playerFilename,
    DROPS_X_FRAME_COUNT,
    DROPS_Y_FRAME_COUNT
);
const VGCVector     frameIndex = VGCVector(0, 0);
const VGCVector     position   = VGCVector(xPos, yPos);
const VGCAdjustment adjustment = VGCAdjustment(0.0, 0.0);
VGCDisplay::renderImage(player, frameIndex, position, adjustment);
VGCDisplay::closeImage(player);

};

As you can see drawEnemy gets called quite a lot which slows down my game but I'm not sure on how to avoid this function getting called so many times.