Quartz2d: how to change the IOS default context coordinate system to the quartz Normal Coordinate System

Because the origin of the default Coordinate System of IOS uikit is in the upper left corner of the view rectangle, the origin of the quartz coordinate system is usually in the lower left corner. Therefore, when using qaurtz to process graphics, we often need to convert the coordinate system to a State consistent with that of quartz:

Void translatecoordsystem (cgcontextref context, cgrect viewframe) {cgcontexttranslatectm (context, 0.0f, viewframe. Size. Height); cgcontextscalectm (context, 1.0f,-1.0f );}

In this way, you can draw normally. Otherwise, the image is drawn in the default mode, and the image is displayed upside down.