Android : Android pixcel to dpi

final float scale = getContext().getResources().getDisplayMetrics().density;

final float densityDpi = getContext().getResources().getDisplayMetrics().densityDpi;

float pxPerInch = 340; // default value - note it's a new density in API version 9.
switch(densityDpi){
     case DisplayMetrics.DENSITY_LOW:
                 pxPerInch = 120 * scale;
                 break;
     case DisplayMetrics.DENSITY_MEDIUM:
                 pxPerInch = 160 * scale;
                 break;
     case DisplayMetrics.DENSITY_HIGH:
                 pxPerInch = 240 * scale;
                 break;
}

출처 : http://blog.naver.com/lowmans/100123712145