Ipad and RGB/32 issues

[NotMyFault]

Hi,

 

these are maybe multiple issues, but all in the same area:

• iPad is unable to create a new document with RGB/32
• (you can convert from 16 to 32 after creating RGB/16)
• iPad is unable to export as png with RGB/32
• (if you try you get RGB/16 instead)

As this happens for new files, i don’t upload a test image.

 

[Dan C]

Hi @NotMyFault,

Thanks for your report!

I can confirm the first issue is already logged with our devs, I'll get this bumped now.

Regarding the second report, this is the correct behaviour - both the Affinity desktop and iPad apps export PNG in 24bit + 8 bit alpha when transparency is present.

I hope this helps

[walt.farrell]

26 minutes ago, Dan C said:

both the Affinity desktop and iPad apps export PNG in 24bit + 8 bit alpha when transparency is present.

That is fine for RGB/8 images, but the report was about RGB/32 images.

[NotMyFault]

12 minutes ago, walt.farrell said:

That is fine for RGB/8 images, but the report was about RGB/32 images.

It seems Dan C gave the correct answer (as almost every time).

PNG actually does not support RGB/32, with or without alpha channel. 
I failed to check this before posting.

https://en.wikipedia.org/wiki/Portable_Network_Graphics

Pixel format[edit]

PNG color type^[9]

Color type	Channels	Bits per channel
		1	2	4	8	16
Indexed	1	1	2	4	8
Grayscale	1	1	2	4	8	16
Grayscale and alpha	2				16	32
Truecolor	3				24	48
Truecolor and alpha	4				32	64

Pixels in PNG images are numbers that may be either indices of sample data in the palette or the sample data itself. The palette is a separate table contained in the PLTE chunk. Sample data for a single pixelconsists of a tuple of between one and four numbers. Whether the pixel data represents palette indices or explicit sample values, the numbers are referred to as channels and every number in the image is encoded with an identical format.

The permitted formats encode each number as an unsigned integer value using a fixed number of bits, referred to in the PNG specification as the bit depth. Notice that this is not the same as color depth, which is commonly used to refer to the total number of bits in each pixel, not each channel. The permitted bit depths are summarized in the table along with the total number of bits used for each pixel.