The impressionist style of painting is characterized chiefly

The impressionist style of painting 主语：印象派的绘画风格
is characterized 谓语：特征是；以.为特征
by concentration on the general impression produced by a scene or object and the use of unmixed primary colors and small strokes to simulate actual reflected light.介词短语作状语.其中produced by a scene or object 过去分词短语作后置定语修饰impression；动词不定式短语 to simulate actual reflected light.作目的状语.
全句的意思：印象派绘画风格的特征在于其对景色和物体所产生的总印象的关注以及为了模拟实际反射的光线而采用的纯原色和细微的笔触.