I want to be able to scale and position an image, and then save just part of that image. I currently have a UIImageView inside a UIScrollView. After zooming and positioning the image I hit a button and then have the following code.
// imageScale = current scale of UIView
// get the new width and height of the scaled UIView
float scaledImageWidth = [scrollView viewWithTag:1].frame.size.width;
float scaledImageHeight = [scrollView viewWithTag:1].frame.size.height;
// get starting X and Y coords of target in relation to UIView
// target is a box in the middle of the screen, 210x255px
float imageY = scaledImageHeight / 2 - (scrollView.contentOffset.y * imageScale);
imageY = (imageY < 0) ? (140 * imageScale) + ((imageY * -1) + (scrollView.contentOffset.y *imageScale)) : (140 * imageScale) - imageY;
float imageX = scaledImageWidth / 2 - (scrollView.contentOffset.x * imageScale);
imageX = (imageX < 0) ? (56 * imageScale) + ((imageX * -1) + (scrollView.contentOffset.x *imageScale)) : (56 * imageScale) - imageX;
// image = original unscaled UIImage
// create new UIImage that matches the size of the scaled UIView we have been working with
UIGraphicsBeginImageContext( CGSizeMake(scaledImageWidth, scaledImageHeight) );
[image drawInRect:CGRectMake(0,0,scaledImageWidth, scaledImageHeight)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// now with the UIImage that is the size we want, copy a piece of the image
CGImageRef imageRef = CGImageCreateWithImageInRect([newImage CGImage], CGRectMake(imageX,imageY,210, 255));
UIImage* myThumbnail = [UIImage imageWithCGImage:imageRef];
CGImageRelease(imageRef);
This seems to work mostly ok. The problem I see is that when I make the final copy of just a piece of the image, the copy (myThumbnail) isn't scaled. However, the source (newImage) appears to scale without problems. Does anyone know what I am missing, or if there would be a different approach to this problem?
Edit:
Ok, I was a little off. The copy is scaling. The problem I'm having is its position is off. So if the image position is too far in one direction, the new copy wont be in the right position. For example, if I move the image so that I'm cropping the bottom left, it might give me a sliver on the right instead of that bottom left portion of the image.
Related
I've an UIImageView with content mode Aspect Fit of size 220x155. I'm dynamically inserting different images in different resolutions, but all larger than the size of the UIImageView. As the content mode is set to Aspect Fit, the image is scaled with respect to the ratio to fit the UIImageView.
My problem is, that if for instance the image inside the UIImageView is scaled to 220x100, I would like the UIImageView to shrink from a height of 155 to 100 too to avoid space between my elements.
How can I do this?
I wrote this method to get me the frame of the image view once it loaded an image.
So , the requirements for me were the same as in your case:
1) image view with aspect fit content mode
2) get the exact frame of the image ( this way you can re-position the image view )
Hope this helps:
- (CGRect) getFrameOfImage:(AsyncImageView *) imgView
{
if(!imgView.loaded)
return CGRectZero;
CGSize imgSize = imgView.image.size;
CGSize frameSize = imgView.frame.size;
CGRect resultFrame;
if(imgSize.width < frameSize.width && imgSize.height < frameSize.height)
{
resultFrame.size = imgSize;
}
else
{
float widthRatio = imgSize.width / frameSize.width;
float heightRatio = imgSize.height / frameSize.height;
float maxRatio = MAX (widthRatio , heightRatio);
NSLog(#"widthRatio = %.2f , heightRatio = %.2f , maxRatio = %.2f" , widthRatio , heightRatio , maxRatio);
resultFrame.size = CGSizeMake(imgSize.width / maxRatio, imgSize.height / maxRatio);
}
resultFrame.origin = CGPointMake(imgView.center.x - resultFrame.size.width/2 , imgView.center.y - resultFrame.size.height/2);
return resultFrame;
}
I am using here AsyncImageView but it will work just as good with UIImageView. The important thing to remember is to call this method AFTER the image was loaded.
Cheers!
Its very simple, you just need to get image actual size, which can be done by
UIImage *image = [UIImage imageName:#""];
then you just need to set frame
Like :-
imageView.frame = CGRectMake(0.0, 0.0, image.size.width, image.size.height);
Hope this helps you.
Once the imageview's image is set to the new image (and thus scaled) you can get the height of the image inside the imageview (imageview.image.size.height) and set the imageview's height (frame) accordingly.
I am trying to to pixel-by-pixel image filters using Core Graphics (breaking a CGImage into unsigned integers using CFData)
When I try to create an imaged with the processed data, however, the resulting image comes out with significantly different colors.
I commented out the entire loop where I actually alter the pixels' rgb values and nothing changes, either.
When I initialize the UIImage I am using in the filter; I do a resize using drawInRect with UIGraphicsBeginContext(); on an image taken from the camera.
When I remove the resize step and set my image directly from the camera; the filters seem to work just fine. Here's the code where I initialize the image I am using (from inside didFinishPickingImage)
self.editingImage is a UIImageView and self.editingUIImage is a UIImage
-(void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingImage : (UIImage *)image
editingInfo:(NSDictionary *)editingInfo
{
self.didAskForImage = YES;
UIGraphicsBeginImageContext(self.editingImage.frame.size);
float prop = image.size.width / image.size.height;
float left, top, width, height;
if(prop < 1){
height = self.editingImage.frame.size.height;
width = (height / image.size.height) * image.size.width;
left = (self.editingImage.frame.size.width - width)/2;
top = 0;
}else{
width = self.editingImage.frame.size.width;
height = (width / image.size.width) * image.size.height;
top = (self.editingImage.frame.size.height - height)/2;
left = 0;
}
[image drawInRect:CGRectMake(left, top, width, height)];
self.editingUIImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.editingImage.image = self.editingUIImage;
[self.contrastSlider addTarget:self action:#selector(doImageFilter:) forControlEvents:UIControlEventValueChanged];
[self.brightnessSlider addTarget:self action:#selector(doImageFilter:) forControlEvents:UIControlEventValueChanged];
[picker dismissModalViewControllerAnimated:YES];
picker = nil;
}
The resizes the image just the way I need it as far as position;
Here's the image filtering function, I've taken the actual loop contents out because they're irrelevant.
- (void) doImageFilter:(id)sender{
CGImageRef src = self.editingUIImage.CGImage;
CFDataRef dta;
dta = CGDataProviderCopyData(CGImageGetDataProvider(src));
UInt8 *pixData = (UInt8 *) CFDataGetBytePtr(dta);
int dtaLen = CFDataGetLength(dta);
for (int i = 0; i < dtaLen; i += 3) {
//the loop
}
CGContextRef ctx;
ctx = CGBitmapContextCreate(pixData, CGImageGetWidth(src), CGImageGetHeight(src), 8, CGImageGetBytesPerRow(src), CGImageGetColorSpace(src), kCGImageAlphaPremultipliedLast);
CGImageRef newCG = CGBitmapContextCreateImage(ctx);
UIImage *new = [UIImage imageWithCGImage:newCG];
CGContextRelease(ctx);
CFRelease(dta);
CGImageRelease(newCG);
self.editingImage.image = new;
}
The image looks like this at first
and then after doing doImageFilter...
As mentioned before, this only happens when I use the resize method shown above.
Really stumped on this one, been researching it all day... any help very appreciated!
Cheers
Update: I've examined all the image objects' color spaces and they're all kCGColorSpaceDeviceRGB. Pretty stumped on this one guys, I'm pretty some something is going wrong when I break the image into unsigned integers, but I'm not sure what.. Anyone?
Your problem is on the last line:
ctx = CGBitmapContextCreate(pixData,
CGImageGetWidth(src),
CGImageGetHeight(src),
8,
CGImageGetBytesPerRow(src),
CGImageGetColorSpace(src),
kCGImageAlphaPremultipliedLast);
You're making an assumption about the alpha and the component ordering of the data of the source image, which is apparently not correct. You should get that from the source image via CGImageGetBitmapInfo(src).
To avoid issues like this one, if you're starting with an arbitrary CGImage and you want to manipulate the bytes of the bitmap directly, it is best to make a CGBitmapContext in a format that you specify yourself (not directly taken from the source image). Then, draw your source image into the bitmap context; CG will convert the image's data into your bitmap context's format, if necessary. Then get the data from the bitmap context and manipulate it.
i use this code to get image from facebook profile and show it on UIImageView
// Get the profile image
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[result objectForKey:#"pic"]]]];
// Resize, crop the image to make sure it is square and renders
// well on Retina display
float ratio;
float delta;
float px = 100; // Double the pixels of the UIImageView (to render on Retina)
CGPoint offset;
CGSize size = image.size;
if (size.width > size.height) {
ratio = px / size.width;
delta = (ratio*size.width - ratio*size.height);
offset = CGPointMake(delta/2, 0);
} else {
ratio = px / size.height;
delta = (ratio*size.height - ratio*size.width);
offset = CGPointMake(0, delta/2);
}
CGRect clipRect = CGRectMake(-offset.x, -offset.y,
(ratio * size.width) + delta,
(ratio * size.height) + delta);
UIGraphicsBeginImageContext(CGSizeMake(px, px));
UIRectClip(clipRect);
[image drawInRect:clipRect];
UIImage *imgThumb = UIGraphicsGetImageFromCurrentImageContext();
[imgThumb retain];
imageFb=imgThumb;
[profilePhotoImageView setImage:imgThumb];
I want to make a button, when clicked allows the user to change the image by an image in the library of the iPhone (photos he took with the iphone ..) . I have no idea how I should proceed, help please
Access to the user's photo library is most easily mediated with the use of UIImagePickerController. You create and configure and instance, set a delegate and display it modally. Implement -imagePickerController:didFinishPickingMediaWithInfo to be notified when the user selects an image. You can then persist this image in the user's documents directory.
UIImagePickerController Class Reference
basically I am making an app that involves a user taking a photo, or selecting one already on their device, and then placing an overlay onto the image.
So, I seem to have coded everything fine, apart from one thing, after the user has selected the overlay and positioned it, when saved the size of the overlay has changed, whereas the x and y values seem correct.
And so this is the code I use to add the overlay ("image" being the users photo):
float wid = (overlay.image.size.width);
float hei = (overlay.image.size.height);
overlay.frame = CGRectMake(0, 0, wid, hei);
[image addSubview:overlay];
And this is the code used to save the resulting image:
UIGraphicsBeginImageContext(image.image.size);
// Draw the users photo
[image.image drawInRect:CGRectMake(0, 0, image.image.size.width, image.image.size.height)];
// Draw the overlay
float xx = (overlay.center.x);
float yy = (overlay.center.y);
CGRect aaFrame = overlay.frame;
float width = aaFrame.size.width;
float height = aaFrame.size.height;
[overlay.image drawInRect:CGRectMake(xx, yy, width, height)];
UIGraphicsEndImageContext();
Any help? Thanks
The problem is that you are using image's size rather than the image view's frame size. Image seems to be much larger than its image view so when you use the image's size the other image's size ends up being much smaller in comparison although it is still the correct size. You can modify your snippet to this –
UIGraphicsBeginImageContext(image.frame.size);
// Draw the users photo
[image.image drawInRect:CGRectMake(0, 0, image.frame.size.width, image.frame.size.height)];
[overlay.image drawInRect:overlay.frame];
UIImage * resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Avoiding loss of quality
While the above method leads to loss of resolution, trying to draw the parent image in its proper resolution might have an unwanted effect on its child image i.e. if the overlay wasn't of high resolution itself then it can end being stretchy. However you can try this code to draw it in the parent image's resolution (untested, let me know if you've problems ) –
float verticalScale = image.image.size.height / image.frame.size.height;
float horizontalScale = image.image.size.width / image.frame.size.width;
CGRect overlayFrame = overlay.frame;
overlayFrame.origin.x *= horizontalScale;
overlayFrame.origin.y *= verticalScale;
overlayFrame.size.width *= horizontalScale;
overlayFrame.size.height *= verticalScale;
UIGraphicsBeginImageContext(image.image.size);
// Draw the users photo
[image.image drawInRect:CGRectMake(0, 0, image.image.size.width, image.image.size.height)];
[overlay.image drawInRect:overlayFrame];
UIImage * resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
Given a UIImage of any dimension, I wish to generate a square "icon" sized version, px pixels to a side, without any distortion (stretching). However, I'm running into a little snag. Not quite sure where the problem is. Here's what I'm doing so far.
First, given a UImage size, I determine three things: the ratio to use when scaling down the image; a delta (the difference between our desired icon size and the longest side), and an offset (which is used to figure out our origin coordinate when clipping the image):
if (size.width > size.height) {
ratio = px / size.width;
delta = (ratio*size.width - ratio*size.height);
offset = CGPointMake(delta/2, 0);
} else {
ratio = px / size.height;
delta = (ratio*size.height - ratio*size.width);
offset = CGPointMake(0, delta/2);
}
Now, let's say you have an image 640px wide by 480px high, and we want to get a 50px x 50px icon out of this. The width is greater than the height, so our calculations are:
ratio = 50px / 640px = 0.078125
delta = (ratio * 640px) - (ratio * 480px) = 50px - 37.5px = 12.5px
offset = {x=6.25, y=0}
Next, I create a CGRect rect that is large enough to be cropped down to our desired icon size without distortion, plus a clipRect for clipping purposes:
CGRect rect = CGRectMake(0.0, 0.0, (ratio * size.width) + delta,
(ratio * size.height) + delta);
CGRect clipRect = CGRectMake(offset.x, offset.y, px, px);
Substituting our values from above, we get:
rect = origin {x=0.0, y=0.0}, size {width=62.5, height=50.0}
clipRect = origin {x=6.25, y=0}, size {width=50.0, height=50.0}
So now we have a 62.5px wide by 50px high rect to work with, and a clipping rectangle that grabs the "middle" 50x50 portion.
On to the home stretch! Next, we set up our image context, draw the UIImage (called myImage here) into the rect, set the clipping rectangle, get the (presumably now-clipped) image, use it, and finally clean up our image context:
UIGraphicsBeginImageContext(rect.size);
[myImage drawInRect:rect];
UIRectClip(clipRect);
UIImage *icon = UIGraphicsGetImageFromCurrentImageContext();
// Do something with the icon here ...
UIGraphicsEndImageContext();
Only one problem: The clipping never occurs! I end up with an image 63px wide x 50px high. :(
Perhaps I'm misusing/misunderstanding UIRectClip? I've tried shuffling various things around: swapping the use of rect and clipRect, moving UIRectClip before drawInRect:. No dice.
I tried searching for an example of this method online as well, to no avail. For the record, UIRectClip is defined as:
Modifies the current clipping path by
intersecting it with the specified
rectangle.
Shuffling things around gets us a little bit closer:
UIGraphicsBeginImageContext(clipRect.size);
UIRectClip(rect);
[myImage drawInRect:rect];
Now we don't have distortion, but the clipped image isn't centered on the original as I expected. Still, at least the image is 50x50, though the variable names are now fouled up as a result of said shuffling. (I'll respectfully leave renaming as an exercise for the reader.)
Eureka! I had things a little mixed up. This works:
CGRect clipRect = CGRectMake(-offset.x, -offset.y,
(ratio * size.width) + delta,
(ratio * size.height) + delta);
UIGraphicsBeginImageContext(CGSizeMake(px, px));
UIRectClip(clipRect);
[myImage drawInRect:clipRect];
UIImage *icon = UIGraphicsGetImageFromCurrentImageContext();
// Do something with the icon here ...
UIGraphicsEndImageContext();
No more need for rect. The trick appears to be using a negative offset in the clipping rectangle, thereby lining up the origin of where we want to grab our 50 x 50 image (in this example).
Perhaps there's an easier way. If so, please weigh in!
I wanted to achieve a similar thing but found the answer from by the original poster didn't quite work. It distorted the image. This may well be solely because he didn't post the whole solution and had changed some of how the variables are initialised:
(if (size.width > size.height)
ratio = px / size.width;
Was wrong for my solution (which wanted to use the largest possible square from the source image). Also it is not necessary to use UIClipRect - if you make the context the size of the image you want to extract, no actual drawing will be done outside that rect anyway. It is just a matter of scaling the size of the image rect and offsetting one of the origin coordinates. I have posted my solution below:
+(UIImage *)makeIconImage:(UIImage *)image
{
CGFloat destSize = 400.0;
CGRect rect = CGRectMake(0, 0, destSize, destSize);
UIGraphicsBeginImageContext(rect.size);
if(image.size.width != image.size.height)
{
CGFloat ratio;
CGRect destRect;
if (image.size.width > image.size.height)
{
ratio = destSize / image.size.height;
CGFloat destWidth = image.size.width * ratio;
CGFloat destX = (destWidth - destSize) / 2.0;
destRect = CGRectMake(-destX, 0, destWidth, destSize);
}
else
{
ratio = destSize / image.size.width;
CGFloat destHeight = image.size.height * ratio;
CGFloat destY = (destHeight - destSize) / 2.0;
destRect = CGRectMake(0, destY, destSize, destHeight);
}
[image drawInRect:destRect];
}
else
{
[image drawInRect:rect];
}
UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return scaledImage;
}
wheeliebin answers is correct but he forgot a minus sign in front of destY
destRect = CGRectMake(0, -destY, destSize, destHeight);