Best range of filter value in CIfilter

Question

I'm developing an iOS application using the CoreImage framework where a user can apply a certain set of photo filters like brightness, contrast, saturation, etc.

Up to now my application is functionally working fine with each filter but its not doing attractive image editing.

I have two questions.

Q1. What should be the best range of values for each filter?

Q2. Is there any way to get current contrast or brightness value of UIImage?

Answer 1

There is no Best range of values for each filter. Its all depend on your requirement that how much range of value needed. For example contrast can be 0.0 to 1.0 and whatever your app need is to set contrast value in between 0.0 to 1.0. Same is applied on all other filters while changing or manipulating RGB or CMYK or RYB pixel values.

You cannot get current contrast and brightness of a image because whatever the value of contrast & Brightness is set is the current B & C of Image.

Also it depends of Image. If an Image is captured in a dark place you need to set high brightness and contrast like 0.8 or 0.7. But if an Image is captured in a day time with presence of light the either there is no need to set brightness or contrast or need to set minimum valiu like 0.2 or 0.3.

And for Image Editing or Applying Image Filters the Best library i have got is GPUImage