The solution is simple:
- Use “pixel-perfect” image
Image should be same size as the image view. Because if the size does not match, the iOS will calculate the “intermediate” pixels for you. They are just approximation and blur your image.
- Use PNG
JPG is lossy format. Its algorithm is effective for photo but bad for text/vector shape. Because it handles badly on some sharp border. If you observe the text on JPEG, you can find some “distortion” (artifact) around them. (look 1) PNG can handle such things well. But it will increase the image size.
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