iOS - Points to pixels and Pixels to points conversion

pointsPixels.m

- (CGFloat)pixelToPoints:(CGFloat)px {
    CGFloat pointsPerInch = 72.0; // see: http://en.wikipedia.org/wiki/Point%5Fsize#Current%5FDTP%5Fpoint%5Fsystem
    CGFloat scale = 1;
    float pixelPerInch; // DPI
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        pixelPerInch = 132 * scale;
    } else if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
        pixelPerInch = 163 * scale;
    } else {
        pixelPerInch = 160 * scale;
    }
    CGFloat points = px * pointsPerInch / pixelPerInch;
    return points;
}

- (CGFloat)pointsToPixels:(CGFloat)points {
    CGFloat pointsPerInch = 72.0; // see: http://en.wikipedia.org/wiki/Point%5Fsize#Current%5FDTP%5Fpoint%5Fsystem
    CGFloat scale = 1;
    float pixelPerInch; // DPI
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        pixelPerInch = 132 * scale;
    } else if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone) {
        pixelPerInch = 163 * scale;
    } else {
        pixelPerInch = 160 * scale;
    }
    CGFloat px = points / pointsPerInch * pixelPerInch;
    return px;
}