问题
I've read some posts which recommend the use of:
UIGraphicsBeginImageContextWithOptions((image.size), NO, 0.0f)
instead of:
UIGraphicsBeginImageContext(image.size).
Because the first one uses Retina-scale when drawing, otherwise you get blocky images.
I'm a little confused about when to use or not the retina-scale option.
If i have a photograph which is 1000x1000 px, and i call UIGraphicsBeginImageContext passing those dimensions, am i not specifying exactly how many points i want to draw? Is that ok?
Or should i call UIGraphicsBeginImageContextWithOptions passing half the dimensions (500x500px)? Does it make any difference?
回答1:
You can get the scale value of your device by the following method
[[UIScreen mainScreen] scale]
With this information you can decide how many points you would like to draw.
回答2:
You can create the image context like this:
UIGraphicsBeginImageContextWithOptions(size, false, UIScreen.mainScreen().scale)
来源：https://stackoverflow.com/questions/11603212/uigraphicsbeginimagecontext-must-be-retina-aware