Right, I understand conceptually what needs to happen. It is the actual implementation where I’m getting stuck.
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. 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. Thanks again, Nevin On Wed, Mar 15, 2017 at 1:44 PM, Jens Alfke <j...@mooseyard.com> wrote: > > On Mar 15, 2017, at 9:56 AM, Nevin Brackett-Rozinsky via swift-users < > swift-users@swift.org> wrote: > > For one of my programs, I need to take an array of Floats and use the > underlying bytes as the RGBA data for a bitmap image. In particular, the 32 > bits of each Float must be treated as the color of the corresponding pixel. > So the result is an image of height 1 and width the length of the array. > > > Make a pixmap, an array of UInt8 that’s 4x longer than your original > array, where the elements are interpreted as R, G, B, A, R, G, B, A… Then > fill it in based on the original float values. > > In particular, I need to be able to save the image as a PNG file, then > later load it from disk and reconstruct each Float from its pixel, with no > loss or change to the value of the Floats. So, how do I go from [Float] to > a bitmap image suitable for saving to disk, without altering the underlying > bytes? > > > You’ll need to call some external image-encoding library, passing it your > pixmap. If you’re on an Apple platform try ImageIO. If not, or if you want > to be cross-platform, try libpng. > > —Jens >
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