[image_picker] Fix images changing to incorrect orientation

[vashworth]

When you take an image with an iPhone in portrait mode, it's actually taking the image in landscape mode and saving rotation information into the image's metadata. The UIImage class will then automatically transform the image to be the correct orientation. You can read more about it here.

Now, in the plugin code, when the user resizes an image that has orientation metadata, we resize it differently to handle the rotation.

plugins/packages/image_picker/image_picker_ios/ios/Classes/FLTImagePickerImageUtil.m

Lines 86 to 105 in d699b4a

	// Scaling the image always rotate itself based on the current imageOrientation of the original
	// Image. Set to orientationUp for the orignal image before scaling, so the scaled image doesn't
	// mess up with the pixels.
	UIImage *imageToScale = [UIImage imageWithCGImage:image.CGImage
	scale:1
	orientation:UIImageOrientationUp];
	// The image orientation is manually set to UIImageOrientationUp which swapped the aspect ratio in
	// some scenarios. For example, when the original image has orientation left, the horizontal
	// pixels should be scaled to `width` and the vertical pixels should be scaled to `height`. After
	// setting the orientation to up, we end up scaling the horizontal pixels to `height` and vertical
	// to `width`. Below swap will solve this issue.
	if ([image imageOrientation] == UIImageOrientationLeft ||
	[image imageOrientation] == UIImageOrientationRight ||
	[image imageOrientation] == UIImageOrientationLeftMirrored ||
	[image imageOrientation] == UIImageOrientationRightMirrored) {
	double temp = width;
	width = height;
	height = temp;
	}

#7084 changed the plugin so that every image returns basic metadata, which includes the orientation/rotation info. However, it wasn't doing to metadata scaling process which was causing the images to get incorrect orientation.

Fixes flutter/flutter#120356.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[vashworth]

@cyanglaz @jmagman Any ideas on how to test this? I could use a real image to test it, but I'm struggling to get a small image with the orientation metadata in it. For example, I can take a picture on my iPhone and it will have the orientation data in it and is 260KB. If I resize it or compress it, it loses the orientation metadata.

[jmagman]

@cyanglaz @jmagman Any ideas on how to test this? I could use a real image to test it, but I'm struggling to get a small image with the orientation metadata in it. For example, I can take a picture on my iPhone and it will have the orientation data in it and is 260KB. If I resize it or compress it, it loses the orientation metadata.

Can you re-add the orientation metadata with something like exiftool? There also might be some imagemagick flags that resize/compress without stripping the metadata.

[jmagman]

LGTM

[jmagman]

LGTM

Once the formatter is happy.