From 01a93998f24d113e39638f8a6fef99a7e8cdd22e Mon Sep 17 00:00:00 2001
From: Joaquim <jluis@ualg.pt>
Date: Mon, 22 Apr 2024 15:55:34 +0100
Subject: [PATCH] Add a 'grays2rgb' function to compose three gray images into
 a RGB.

---
 src/GMT.jl         |  2 +-
 src/utils_types.jl | 31 +++++++++++++++++++++++++++++++
 test/test_misc.jl  |  4 ++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/GMT.jl b/src/GMT.jl
index a199fada2..b82b9155f 100644
--- a/src/GMT.jl
+++ b/src/GMT.jl
@@ -171,7 +171,7 @@ export
 
 	VSdisp, mad, info, kmeans, pca, mosaic, quadbounds, quadkey, geocoder, getprovider,
 
-	binarize, isodata, rgb2gray, grid2img, img2grid,
+	binarize, isodata, rgb2gray, grid2img, img2grid, grays2rgb,
 
 	Ginnerjoin, Gouterjoin, Gleftjoin, Grightjoin, Gcrossjoin, Gsemijoin, Gantijoin, spatialjoin,
 
diff --git a/src/utils_types.jl b/src/utils_types.jl
index c6d0e76b8..08a8b0e51 100644
--- a/src/utils_types.jl
+++ b/src/utils_types.jl
@@ -1813,6 +1813,37 @@ function ind2rgb(I::GMTimage, cmap::GMTcpt=GMTcpt(), layout="BRPa")
 	mat2img(imgRGB, x=I.x, y=I.y, proj4=I.proj4, wkt=I.wkt, mem_layout=layout, is_transposed=istransposed)
 end
 
+# ----------------------------------------------------------------------------------------------------------
+"""
+    I = grays2rgb(bandR, bandG, bandB, GI=nothing) -> GMTimage
+
+Take three grayscale images as UInt8 matrices or GMTimages and compose an RGB image by simply copying
+the values of each band into the respective color channel of the output image. When the inputs are UInt8
+matrices optionally provide a GMTgrid or GMTimage as fourth argument to set georeferencing info on output.
+The output is always a GMTimage object.
+
+Note, do not confuse this function with `ind2rgb` that takes a single indexed image and creates a RGB
+using the image's colormap.
+
+### Example
+```juliadoc
+I1 = mat2img(rand(UInt8, 16,16)); I2 = mat2img(rand(UInt8, 16,16)); I3 = mat2img(rand(UInt8, 16,16));
+Irgb = grays2rgb(I1,I2,I3)
+```
+"""
+function grays2rgb(bandR::GMTimage{UInt8,2}, bandG::GMTimage{UInt8,2}, bandB::GMTimage{UInt8,2})
+	@assert size(bandR) == size(bandG) == size(bandB)
+	img = Array{UInt8}(undef, size(bandR,1), size(bandR,2), 3)
+	img[:,:,1] .= bandR.image;		img[:,:,2] .= bandG.image;		img[:,:,3] .= bandB.image
+	mat2img(img, bandR)
+end
+function grays2rgb(bandR::Matrix{UInt8}, bandG::Matrix{UInt8}, bandB::Matrix{UInt8}, GI::Union{GItype, Nothing}=nothing)
+	@assert size(bandR) == size(bandG) == size(bandB)
+	img = Array{UInt8}(undef, size(bandR,1), size(bandR,2), 3)
+	img[:,:,1] .= bandR;		img[:,:,2] .= bandG;		img[:,:,3] .= bandB
+	return GI !== nothing ? mat2img(img, GI) : mat2img(img)
+end
+
 # ---------------------------------------------------------------------------------------------------
 """
     G = mat2grid(mat; reg=nothing, x=[], y=[], v=[], hdr=[], proj4::String="", wkt::String="",
diff --git a/test/test_misc.jl b/test/test_misc.jl
index d094b1eca..6c9b44522 100644
--- a/test/test_misc.jl
+++ b/test/test_misc.jl
@@ -227,6 +227,10 @@
 	mask[1] = 100;		# Force variable mask
 	image_alpha!(img, alpha_band=mask, burn=(0,255,0))
 
+	I1 = mat2img(rand(UInt8, 16,16)); I2 = mat2img(rand(UInt8, 16,16)); I3 = mat2img(rand(UInt8, 16,16));
+	grays2rgb(I1,I2,I3);
+	grays2rgb(I1.image,I2.image,I3.image);
+
 	GMT.resetGMT()
 	try
 		upGMT()