Powertips » UIImage

How to get new image size in UIImageView

admin — Mon, 09 Apr 2012 14:59:32 +0000

Sometime we need to know the new size of the image that’s being rendered in UIImageView with auto scaled applied. Here’s the computation

-(CGRect)frameForImage:(UIImage*)image inImageViewAspectFit:(UIImageView*)imageView
{
float imageRatio = image.size.width / image.size.height;

float viewRatio = imageView.frame.size.width / imageView.frame.size.height;

if(imageRatio < viewRatio)
{
float scale = imageView.frame.size.height / image.size.height;

float width = scale * image.size.width;

float topLeftX = (imageView.frame.size.width - width) * 0.5;

return CGRectMake(topLeftX, 0, width, imageView.frame.size.height);
}
else
{
float scale = imageView.frame.size.width / image.size.width;

float height = scale * image.size.height;

float topLeftY = (imageView.frame.size.height - height) * 0.5;

return CGRectMake(0, topLeftY, imageView.frame.size.width, height);
}

}

Source

How to save UIImage to application document in IOS

admin — Fri, 09 Mar 2012 16:09:17 +0000

Here’s a sample snippet on how to save image to application document.

- (void)saveUIImage:(UIImage *)image withName:(NSString *)name {
NSData *imgData = UIImageJPEGRepresentation(image, 1.0);
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:name];
[fileManager createFileAtPath:fullPath contents:imgData attributes:nil];
}

How to flip UIImage

admin — Sun, 07 Aug 2011 13:04:17 +0000

UIImage* sourceImage = [UIImage imageNamed:@"whatever.png"];

UIImage* flippedImage = [UIImage imageWithCGImage:sourceImage.CGImage scale:1.0 orientation: UIImageOrientationUpMirrored];

Constants:

UIImageOrientation

Specifies the possible orientations of an image.

typedef enum {
   UIImageOrientationUp,
   UIImageOrientationDown,   // 180 deg rotation
   UIImageOrientationLeft,   // 90 deg CCW
   UIImageOrientationRight,   // 90 deg CW
   UIImageOrientationUpMirrored,    // as above but image mirrored along
   // other axis. horizontal flip
   UIImageOrientationDownMirrored,  // horizontal flip
   UIImageOrientationLeftMirrored,  // vertical flip
   UIImageOrientationRightMirrored, // vertical flip
} UIImageOrientation;

Read More at ios developer reference