UIImage resize (Scale proportion) [duplicate] - iphone

Question

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Resize UIImage with aspect ratio?
The following piece of code is resizing the image perfectly, but the problem is that it messes up the aspect ratio (resulting in a skewed image). Any pointers?
// Change image resolution (auto-resize to fit)
+ (UIImage *)scaleImage:(UIImage*)image toResolution:(int)resolution {
CGImageRef imgRef = [image CGImage];
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGRect bounds = CGRectMake(0, 0, width, height);
//if already at the minimum resolution, return the orginal image, otherwise scale
if (width <= resolution && height <= resolution) {
return image;
} else {
CGFloat ratio = width/height;
if (ratio > 1) {
bounds.size.width = resolution;
bounds.size.height = bounds.size.width / ratio;
} else {
bounds.size.height = resolution;
bounds.size.width = bounds.size.height * ratio;
}
}
UIGraphicsBeginImageContext(bounds.size);
[image drawInRect:CGRectMake(0.0, 0.0, bounds.size.width, bounds.size.height)];
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageCopy;
}

Answer 1

I used this single line of code to create a new UIImage which is scaled. Set the scale and orientation params to achieve what you want. The first line of code just grabs the image.
// grab the original image
UIImage *originalImage = [UIImage imageNamed:#"myImage.png"];
// scaling set to 2.0 makes the image 1/2 the size.
UIImage *scaledImage =
[UIImage imageWithCGImage:[originalImage CGImage]
scale:(originalImage.scale * 2.0)
orientation:(originalImage.imageOrientation)];

Answer 2

That's ok not a big problem . thing is u got to find the proportional width and height
like if size is 2048.0 x 1360.0 which has to be resized to 320 x 480 resolution then the resulting image size should be 722.0 x 480.0
here is the formulae to do that . if w,h is original and x,y are resulting image.
w/h=x/y
=>
x=(w/h)*y;
submitting w=2048,h=1360,y=480 => x=722.0 ( here width>height. if height>width then consider x to be 320 and calculate y)
U can submit in this web page . ARC
Confused ? alright , here is category for UIImage which will do the thing for you.
#interface UIImage (UIImageFunctions)
- (UIImage *) scaleToSize: (CGSize)size;
- (UIImage *) scaleProportionalToSize: (CGSize)size;
#end
#implementation UIImage (UIImageFunctions)
- (UIImage *) scaleToSize: (CGSize)size
{
// Scalling selected image to targeted size
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(NULL, size.width, size.height, 8, 0, colorSpace, kCGImageAlphaPremultipliedLast);
CGContextClearRect(context, CGRectMake(0, 0, size.width, size.height));
if(self.imageOrientation == UIImageOrientationRight)
{
CGContextRotateCTM(context, -M_PI_2);
CGContextTranslateCTM(context, -size.height, 0.0f);
CGContextDrawImage(context, CGRectMake(0, 0, size.height, size.width), self.CGImage);
}
else
CGContextDrawImage(context, CGRectMake(0, 0, size.width, size.height), self.CGImage);
CGImageRef scaledImage=CGBitmapContextCreateImage(context);
CGColorSpaceRelease(colorSpace);
CGContextRelease(context);
UIImage *image = [UIImage imageWithCGImage: scaledImage];
CGImageRelease(scaledImage);
return image;
}
- (UIImage *) scaleProportionalToSize: (CGSize)size1
{
if(self.size.width>self.size.height)
{
NSLog(#"LandScape");
size1=CGSizeMake((self.size.width/self.size.height)*size1.height,size1.height);
}
else
{
NSLog(#"Potrait");
size1=CGSizeMake(size1.width,(self.size.height/self.size.width)*size1.width);
}
return [self scaleToSize:size1];
}
#end
-- the following is appropriate call to do this if img is the UIImage instance.
img=[img scaleProportionalToSize:CGSizeMake(320, 480)];

Answer 3

This fixes the math to scale to the max size in both width and height rather than just one depending on the width and height of the original.
- (UIImage *) scaleProportionalToSize: (CGSize)size
{
float widthRatio = size.width/self.size.width;
float heightRatio = size.height/self.size.height;
if(widthRatio > heightRatio)
{
size=CGSizeMake(self.size.width*heightRatio,self.size.height*heightRatio);
} else {
size=CGSizeMake(self.size.width*widthRatio,self.size.height*widthRatio);
}
return [self scaleToSize:size];
}

Answer 4

This change worked for me:
// The size returned by CGImageGetWidth(imgRef) & CGImageGetHeight(imgRef) is incorrect as it doesn't respect the image orientation!
// CGImageRef imgRef = [image CGImage];
// CGFloat width = CGImageGetWidth(imgRef);
// CGFloat height = CGImageGetHeight(imgRef);
//
// This returns the actual width and height of the photo (and hence solves the problem
CGFloat width = image.size.width;
CGFloat height = image.size.height;
CGRect bounds = CGRectMake(0, 0, width, height);

Answer 5

Try to make the bounds's size integer.
#include <math.h>
....
if (ratio > 1) {
bounds.size.width = resolution;
bounds.size.height = round(bounds.size.width / ratio);
} else {
bounds.size.height = resolution;
bounds.size.width = round(bounds.size.height * ratio);
}