Join grayscale image with matrix plot

Question

I have a 200x200 grayscale map map = Image[data, "Byte"] together with a matrix plot path = MatrixPlot[{{0,0,...,0,a,...0},{0,0,...,b,b,b...},...,{a,b,b,...}},ColorRules -> {a -> Black, b -> Green}] that resembles a route in the map.

How can I join both together so that the green route is shown in the map? I tried Show[map,path] but it don't work.

Answer 1

Here is a possible solution. I don't have your matrix describing the route, so I used this random-ish one for the purpose of demonstration:

path={{1,0},{3,1},{5,2},{5,3},{5,4},{8,5},{9,6},{10,7},{11,8},{12,9},{12,10},{13,11},{15,12},{17,13},{18,14},{18,15},{19,16},{19,17},{20,18},{22,19},{24,20},{24,21},{24,22},{25,23},{25,24},{25,25},{26,26},{27,27},{27,28},{28,29},{29,30},{30,31},{31,32},{31,33},{34,34},{36,35},{36,36},{36,37},{38,38},{39,39},{39,40},{40,41},{42,42},{43,43},{45,44},{46,45},{46,46},{48,47},{49,48},{49,49},{53,50},{54,51},{57,52},{58,53},{60,54},{62,55},{62,56},{63,57},{64,58},{64,59},{65,60},{66,61},{66,62},{67,63},{68,64},{72,65},{73,66},{77,67},{77,68},{78,69},{78,70},{79,71},{80,72},{81,73},{84,74},{84,75},{86,76},{88,77},{92,78},{92,79},{93,80},{95,81},{95,82},{96,83},{97,84},{97,85},{98,86},{100,87},{100,88},{102,89},{102,90},{103,91},{103,92},{104,93},{106,94},{106,95},{106,96},{107,97},{107,98},{107,99},{107,100},{108,101},{108,102},{108,103},{108,104},{109,105},{113,106},{115,107},{115,108},{117,109},{119,110},{119,111},{120,112},{120,113},{121,114},{121,115},{123,116},{124,117},{124,118},{124,119},{124,120},{125,121},{127,122},{128,123},{129,124},{130,125},{132,126},{133,127},{133,128},{134,129},{134,130},{136,131},{137,132},{137,133},{137,134},{139,135},{139,136},{142,137},{142,138},{143,139},{143,140},{146,141},{146,142},{146,143},{146,144},{147,145},{148,146},{149,147},{150,148},{151,149},{152,150},{153,151},{154,152},{156,153},{156,154},{157,155},{161,156},{161,157},{167,158},{168,159},{169,160},{170,161},{170,162},{171,163},{171,164},{172,165},{172,166},{173,167},{174,168},{174,169},{174,170},{175,171},{175,172},{175,173},{177,174},{177,175},{178,176},{180,177},{182,178},{186,179},{187,180},{188,181},{188,182},{188,183},{189,184},{190,184}};

t = Normal[SparseArray[path + 1 -> 1, {200, 200}]];

MatrixPlot[t, ColorRules -> {1 -> Green}]

Turn the matrix into an image: i1 = Image[t]

You might want a thicker line: i2 = ImageConvolve[Image[t, "bit"], DiskMatrix[1]]

Change the image to RGB and make the line green: i3 = Image[Map[{#, 1, #} &, ImageData[ColorNegate[i2]], {2}]]

Overlay the path onto the map:ImageCompose[map, SetAlphaChannel[i3, i2]] The alpha channel makes the background of the route image transparent.