Re: Colour operations using CyberShadow's graphics library
On Sunday, 18 January 2015 at 21:10:05 UTC, Phil wrote: Hi, I'm new to D and having a go at writing some image processing stuff using Vladimir's ae.graphics library. To filter (i.e. perform correlations/convolutions) on a view with colour type C, I'd like to perform intermediate calculations using a colour with the same number of channels as C, but all of type double, and then to convert back to something of type C at the end. e.g. for a horizontal blur I'd like to keep a running total per channel, packaged in an all-doubles colour type, and then write (total / kernel width) for each channel back into a value of type C. How do I perform the necessary type magic here? Thanks Hi Phil, The Color template implements opCast for types with the same set of fields, so you should be able to just cast a struct with ubyte fields to one with double fields (or use std.conv.to). The only restriction is that the fields must have the same order. You can use the ChangeChannelType template to create a Color type from an existing one but a different type for the channel fields, for example this assert will hold: static assert(is(ChangeChannelType!(RGB, ushort) == RGB16)); To create a view with double-typed channels from an RGB view, you can use colorMap: alias doubleTypedView = colorMap!(c = cast(ChangeChannelType!(typeof(c), double))c); You can use this as with any other view transform: auto i = onePixel(L8(1)); auto d = i.doubleTypedView(); assert(d[0, 0].l == 1.0); By the way, as I've never tried using floating-point types, the code didn't quite work with them as it is, as some templates expected integral types in a few places. I guess you've fixed things on your side? Anyhow, I've now pushed a commit which fixes and adds tests for FP types.
Re: Colour operations using CyberShadow's graphics library
Brilliant, thanks a lot. That works a treat, allowing me to use c1 + c2 when c1 :: RGB and c2 :: ChangeChannelType!(RGB, int), say. It's not happy with doubles atm, but presumably this is sorted in your push. Thanks again :-) On Monday, 19 January 2015 at 21:11:34 UTC, Vladimir Panteleev wrote: Hi Phil, The Color template implements opCast for types with the same set of fields, so you should be able to just cast a struct with ubyte fields to one with double fields (or use std.conv.to). The only restriction is that the fields must have the same order. You can use the ChangeChannelType template to create a Color type from an existing one but a different type for the channel fields, for example this assert will hold: static assert(is(ChangeChannelType!(RGB, ushort) == RGB16)); To create a view with double-typed channels from an RGB view, you can use colorMap: alias doubleTypedView = colorMap!(c = cast(ChangeChannelType!(typeof(c), double))c); You can use this as with any other view transform: auto i = onePixel(L8(1)); auto d = i.doubleTypedView(); assert(d[0, 0].l == 1.0); By the way, as I've never tried using floating-point types, the code didn't quite work with them as it is, as some templates expected integral types in a few places. I guess you've fixed things on your side? Anyhow, I've now pushed a commit which fixes and adds tests for FP types.
Re: Colour operations using CyberShadow's graphics library
I've done this by declaring a static array of the same length as ViewColor!V.channels, and foreach-ing over the channels in a colour, but this seem uglier than it need to - it would be nice if I could just define + and = appropriately on double[] and colours to do the right thing. On Sunday, 18 January 2015 at 21:10:05 UTC, Phil wrote: Hi, I'm new to D and having a go at writing some image processing stuff using Vladimir's ae.graphics library. To filter (i.e. perform correlations/convolutions) on a view with colour type C, I'd like to perform intermediate calculations using a colour with the same number of channels as C, but all of type double, and then to convert back to something of type C at the end. e.g. for a horizontal blur I'd like to keep a running total per channel, packaged in an all-doubles colour type, and then write (total / kernel width) for each channel back into a value of type C. How do I perform the necessary type magic here? Thanks
Colour operations using CyberShadow's graphics library
Hi, I'm new to D and having a go at writing some image processing stuff using Vladimir's ae.graphics library. To filter (i.e. perform correlations/convolutions) on a view with colour type C, I'd like to perform intermediate calculations using a colour with the same number of channels as C, but all of type double, and then to convert back to something of type C at the end. e.g. for a horizontal blur I'd like to keep a running total per channel, packaged in an all-doubles colour type, and then write (total / kernel width) for each channel back into a value of type C. How do I perform the necessary type magic here? Thanks
