Remove kCGImageSourceShouldCache option when creating image source

[zhongwuzw]

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• I have read and understood the CONTRIBUTING guide

• I have read the Documentation

• I have searched for a similar pull request in the project and found none

• I have updated this branch with the latest master to avoid conflicts (via merge from master or rebase)

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This merge request fixes / reffers to the following issues: ...

Pull Request Description

kCGImageSourceShouldCache is only valid when creating an image from image source, image source would not treat this option. Only kCGImageSourceTypeIdentifierHint can pass to options when creating image source. Please see Documents

[codecov-io]

Codecov Report

Merging #2472 into 5.x will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              5.x    #2472      +/-   ##
==========================================
+ Coverage   77.87%   77.89%   +0.02%     
==========================================
  Files          47       47              
  Lines        6621     6619       -2     
==========================================
  Hits         5156     5156              
+ Misses       1465     1463       -2

Flag	Coverage Δ
#iOS	77.83% <100%> (+0.04%)	⬆️
#macOS	76.65% <100%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
SDWebImage/SDImageAPNGCoder.m	86.72% <100%> (-0.06%)	⬇️
SDWebImage/SDImageGIFCoder.m	87.74% <100%> (+0.34%)	⬆️
SDWebImage/SDAnimatedImage.m	80.4% <0%> (+0.4%)	⬆️

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[dreampiggy]

Emmm...From the documents, the only public options for CGImageSource level, is kCGImageSourceTypeIdentifierHint, it's used to provide information about the image format. That kCGImageSourceShouldCache is only available in CGImageSourceCreateImageAtIndex && CGImageSourceCopyPropertiesAtIndex API. So it's OK to remove it.

I've also check that it indeed behavior. The only available options in CGImageSource level, including the follwings...

• kCGImageSourceTypeIdentifierHint (Public)
• kCGImageSourceShouldMemoryMap (Private)
• kCGImageSourceRespectHEIFFileOrder (Private)
• kCGImageSourceColorTransformAdobeRGBTosRGB (Private)

[zhongwuzw]

@dreampiggy 👍 Yeah, correctly as you said.