Fix broken iOS resize logic

[mono0926]

iOS resize logic was completely broken after #85 merged.

• A. Mistakenly shrank excessively and produced image size was smaller one of Android(correct)
  • Fixed by 0c940af
• B. If original image aspect ratio and minWidth/minHeight is same, it won't be resized
  • Fixed by f3e7071

You can check iOS/Android resized log at example.

For example CompressFile and rotate 180 was pressed, original log was here:

Android(correct)

src width = 4000.0
src height = 2327.0
width scale = 1.7391304
height scale = 1.5513333
scale = 1.5513333
dst width = 2578.4272
dst height = 1500.0

iOS(broken dst size)

width = 4000
height = 2327
minWidth = 2300
minHeight = 1500
format = 0
scale = 0.38
dst width = 1500.00 // Incorrect
dst height = 873.00 // Incorrect

---

For B problem, you can check by modifying https://github.com/OpenFlutter/flutter_image_compress/blob/bc8cd9097d6286cef684f21968fbcb6903aa7fa8/example/lib/main.dart#L269-L270 to this(image size is 1036x1024, so aspect ratio is same):

      minWidth: 518,
      minHeight: 512,

[CaiJingLong]

Thx for PR.

[mono0926]

@CaiJingLong

Thanks for merging.
Could you release this?
https://pub.dev/packages/flutter_image_compress/versions