Rsize photo to 5" height by 4.5" width in iOS 7+

Question

I am developing iphone app in which user can add customize the photo by adding text on it. Now I need to convert this photo into 5" height by 4.5" width in iOS7.

I am taking the screenshot of the the view as below to combine photo & labels added to it as below

-(UIImage*)customizedImageMain
{
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)])
        UIGraphicsBeginImageContextWithOptions(self.containerView.bounds.size, NO, [UIScreen mainScreen].scale);
    else
        UIGraphicsBeginImageContext(self.containerView.bounds.size);
    [self.containerView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *finalImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return finalImage;
}

I checked the image from iPod touch with 4" screen. The image size that I get from above code is nearly 4.445" width & 7.889" height.

Now how can I resize this image to exact 5" height & 4.5" width irrespective of device in which app is running ?

Thanks in advance.

UPDATED Code as per Vin's solution

-(UIImage*)customizedImageFirst
{
    // We want 5" * 4.5" image which can be represented as 1630 * 1458
    // 1630 pixels = 5 inch * (326 pixels / 1 inch)
    // 1458 pixels = 4.5 inch * (326 pixels / 1 inch) in terms of pixels.
    CGSize requiredImageSize = CGSizeMake(1458.0,1630.0);
    UIGraphicsBeginImageContext(requiredImageSize);
    [self.containerView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *combinedImage = UIGraphicsGetImageFromCurrentImageContext();
    [combinedImage drawInRect:CGRectMake(0,0,requiredImageSize.width,requiredImageSize.height)];
    UIImage* finalImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return finalImage;
}

Using above code I am getting this result

Now if I use code without considering UILabels added to customize as below

-(UIImage*)customizedImageSecond  // If I use your code
{
    // We want 5" * 4.5" image which can be represented as 1630 * 1458
    // 1630 pixels = 5 inch * (326 pixels / 1 inch)
    // 1458 pixels = 4.5 inch * (326 pixels / 1 inch) in terms of pixels.
    CGSize requiredImageSize = CGSizeMake(1458.0,1630.0);
    UIGraphicsBeginImageContext(requiredImageSize);
    [self.myImageView.image drawInRect:CGRectMake(0,0,requiredImageSize.width,requiredImageSize.height)];
    UIImage* finalImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return finalImage;
}

, then I am getting this image

My UI hierarchy

Main View of UIViewController. I have added another UIView (containerView) in the main view. In this containerView I have added my UIImageView & UILabels. So get the customized image with labels added on it I am taking the screenshot of containerView.

Answer 1

This is the custom method that i generally use to scale the image to the desired size. This method take the newSize (For Eg : CGSize newSize = CGSizeMake(30.0, 30.0);) as one of the argument. Here, 30.0 is the value in terms of pixels.

+(UIImage*)imageWithImage:(UIImage*)image
              scaledToSize:(CGSize)newSize
{
    UIGraphicsBeginImageContext( newSize );
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

So, you can scale the image in terms of pixels using the above method. But you want to scale the image in terms of inches. A display device has a limited number of pixels it can display, and a limited space over which to display them.

Pixel Density is a measurement of the resolution of devices and can be calculated in terms of PPI(Pixels per inch) or PPCM(Pixels per centimeter).

In your case, you want 5" * 4.5" image which can be represented as 1630 * 1458 (1630 pixels = 5 inch * (326 pixels / 1 inch), 1458 pixels = 4.5 inch * (326 pixels / 1 inch)) in terms of pixels.

Note : PPI for Apple iPhone and iPod Touch above 4th Generation is 326.

So, If you scale the image with size of 1630 * 1458 then you will get the image of 5"" * 4.5". For that you have to pass CGSize newSize = CGSizeMake(1630.0, 1458.0); in above method.