在iOS中更改图像的打印大小

在我的应用程序中，我让用户制作优惠券，预览优惠券，然后他们可以选择打印优惠券。现在，它只是简单地将屏幕向下裁剪，只包括优惠券部分并进行打印，但它打印的是全尺寸的8.5 x 11，并且在这样做时使用了大量墨水，因为优惠券的背景是黑色的。如何将其更改为仅打印纸张的2.5 x 3.5英寸部分

-(void)printer {

    UIPrintInteractionController *controller = [UIPrintInteractionController sharedPrintController];

    if(!controller){

        NSLog(@"Couldn't get shared UIPrintInteractionController!");

        return;

    }

    void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =

    ^(UIPrintInteractionController *printController, BOOL completed, NSError *error) {

        if(!completed && error){

            NSLog(@"FAILED! due to error in domain %@ with error code %u",

                  error.domain, error.code);

        }

    };
    CGRect rect;
    rect=CGRectMake(0, 0, 320, 480);
    UIGraphicsBeginImageContext(rect.size);

    CGContextRef context=UIGraphicsGetCurrentContext();
    [self.tabBarController.view.layer renderInContext:context];

    UIImage *image=UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImage *img = [self cropImage:image rect:CGRectMake(20,70,279,359)];

    UIPrintInfo *printInfo = [UIPrintInfo printInfo];

    printInfo.outputType = UIPrintInfoOutputPhoto;

    printInfo.jobName = @"Your Coupon";

    controller.printInfo = printInfo;

    controller.showsPageRange = YES;



    controller.printingItem = img;



    [controller presentAnimated:YES completionHandler:completionHandler];


}

---

听起来它可以将您打印的图像缩放到输出媒体的全尺寸。您可以尝试将优惠券图像放入一个更大的图像中，然后打印该合成图像。我没有测试此代码，但它是对裁剪图像所做操作的改编

UIImage *img = [self cropImage:image rect:CGRectMake(20,70,279,359)];
// Some size for the full image.
// Obviously you need to experiment with this to get the size right
CGSize targetSize = CGSizeMake(800, 1050);

// This will put the image in the upper left corner
// you could put it in the middle or wherever
CGPoint imageOrigin = CGPointMake(0, 0);
CGRect imageRect = CGRectMake(imageOrigin.x, imageOrigin.y, img.size.width, img.size.height);

// Always scale to the screen scale to get the sharpest images even at the expense of size.
UIGraphicsBeginImageContextWithOptions(targetSize, NO, 0);
[img drawInRect:imageRect];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

// print configuration stuff from your code example goes here...

controller.printingItem = newImage;