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Beginner
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Do IPP Resize functions work with RGBA

Hello,

I am somewhat confused about the IPP Resize functions. For example, the ResizeLinear function supports a mod of 8u_C4R which as I understand is 4 bytes of RGB. I presume the 4th byte is the alpha channel, but I am not sure as other posts suggest that there should be an A in the mod if the function supports alpha channels.

So, in short, are there any IPP resize functions that consider the alpha channel, and resize taking the alpha channel into account, not simply ignoring it? If so, which version of the function is that?

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4 Replies
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New Contributor II
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I thinks the C4R variant will work with premultiplied alpha, as the alpha channel then requieres no special handling.

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Employee
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Hi David,

The 4th channel of C4 is alpha channel. Resize also process alpha channel same as other channels. What the difference of AC4 and C4 is that function for AC4 do not process in alpha channel, but C4 will. Lean more info from link of descriptor.

If you point to use premultiplied alpha that would be used for alpha composition function that when two 4 channel images cover each other, you probably need to calculate alpha(A)*RGB(A)+alpha(B)*RGB(B). But other functions, like resize, the size of alpha also need to be changed by interpolation method. it is not using premultiplied alpha, it process with alpha channel. 

Best regards,
Fiona

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Highlighted
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Hi David,

 

Hope you found the answers informative.

Do you have more questions?

Otherwise, I will close this question ticket.

 

Thank you

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Beginner
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Thanks for the prompt response. We will give it a try. The answer was very helpful.

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