I think I might not be explaining this very well. I want to create a bitmap image where each pixel is RGBA with 8 bits (UInt8) per channel, and I want to specify the exact color for every pixel. I do not know how to do that.
Also, for my specific application, I need to take an array of floating point numbers and say, “Hey, the underlying bits that make up the IEEE-754 representation of these numbers are exactly the bits that I want to use for the colors of the pixels.” I do not know how to do that in Swift. In C I would malloc a buffer, write to it as (float*), then pass it to a function which takes (char*) and saves a PNG. Thus there is only one allocation, the buffer is filled with float values, and the exact bit-pattern is interpreted as RGBA pixels. How can I do the equivalent in Swift? Nevin On Wed, Mar 15, 2017 at 2:43 PM, Jens Alfke <j...@mooseyard.com> wrote: > > On Mar 15, 2017, at 11:07 AM, Nevin Brackett-Rozinsky via swift-users < > swift-users@swift.org> wrote: > > Ideally I’d like to create the bitmap image without having to allocate a > second buffer. The sole purpose of the Float array is for creating this > image, so I’d like to directly use its bytes as the pixels data. I expect > this will involve some Unsafe[…] APIs in Swift, though I don’t know exactly > how. > > > AFAIK there aren’t any pixmap formats that use floats. If you want to > produce ARGB pixels, then emit your data in that format, i.e. as a [UInt8]. > No unsafe stuff needed. > > And yes, I am on an Apple platform. Despite reading boatloads of Core > Graphics documentation, I still can’t make heads or tails out of how to > turn a pre-existing array into the backing data for a bitmap image. This > part is only Swift-related in the sense that I am trying to do it in Swift, > so if there’s a better place to ask/learn about it I’d appreciate being > pointed there. > > > Either Apple’s developer forums, or the cocoa-dev mailing list hosted at > http://lists.apple.com. > > —Jens > >
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