Support for imresize on color images

[fpreiswerk]

My humble attempt to make imresize work on color images.

For an RGB image, b=imresize(a,(new_x, new_y)) does the same as b=imresize(a,(new_x, new_y, 3)). However, if the size of the output color dimension is different from the size of the input color dimension, an error is thrown. For example, the following does not work for the above example: b=imresize(a,(new_x, new_y, 2))

[coveralls]

Coverage decreased (-0.2%) to 78.703% when pulling ae993a7 on fpreiswerk:master into d20aa18 on timholy:master.

[timholy]

Sorry I didn't notice this---I've been pretty preoccupied with #542. I really appreciate this!

One of the things I noted is that this does already work if you represent a color image using a Color type:

julia> using Images, Colors

julia> img = rand(RGB{U8}, 10, 8);

julia> Images.imresize(img, (13, 11))
13×11 Array{ColorTypes.RGB{FixedPointNumbers.UFixed{UInt8,8}},2}:
 RGB{U8}(0.137,0.757,0.133)  RGB{U8}(0.463,0.643,0.227)  …  RGB{U8}(0.569,0.827,0.482)  RGB{U8}(0.082,0.694,0.6)  
 RGB{U8}(0.314,0.365,0.451)  RGB{U8}(0.263,0.298,0.561)     RGB{U8}(0.655,0.51,0.553)   RGB{U8}(0.286,0.502,0.886)
 RGB{U8}(0.416,0.125,0.608)  RGB{U8}(0.431,0.11,0.761)      RGB{U8}(0.733,0.373,0.592)  RGB{U8}(0.659,0.494,0.686)
 RGB{U8}(0.573,0.22,0.529)   RGB{U8}(0.592,0.243,0.69)      RGB{U8}(0.749,0.286,0.541)  RGB{U8}(0.89,0.424,0.439) 
 RGB{U8}(0.918,0.827,0.141)  RGB{U8}(0.361,0.871,0.2)       RGB{U8}(0.635,0.129,0.341)  RGB{U8}(0.659,0.031,0.584)
 RGB{U8}(0.835,0.855,0.675)  RGB{U8}(0.78,0.827,0.302)   …  RGB{U8}(0.573,0.58,0.647)   RGB{U8}(0.855,0.494,0.275)
 RGB{U8}(0.522,0.796,0.443)  RGB{U8}(0.8,0.624,0.239)       RGB{U8}(0.667,0.549,0.502)  RGB{U8}(0.859,0.675,0.486)
 RGB{U8}(0.404,0.671,0.259)  RGB{U8}(0.737,0.522,0.173)     RGB{U8}(0.745,0.408,0.29)   RGB{U8}(0.733,0.592,0.82) 
 RGB{U8}(0.918,0.51,0.941)   RGB{U8}(0.929,0.788,0.282)     RGB{U8}(0.631,0.525,0.408)  RGB{U8}(0.533,0.263,0.871)
 RGB{U8}(0.965,0.247,0.467)  RGB{U8}(0.863,0.435,0.145)     RGB{U8}(0.427,0.545,0.486)  RGB{U8}(0.373,0.161,0.294)
 RGB{U8}(0.91,0.549,0.22)    RGB{U8}(0.722,0.341,0.161)  …  RGB{U8}(0.545,0.337,0.537)  RGB{U8}(0.525,0.259,0.376)
 RGB{U8}(0.69,0.89,0.141)    RGB{U8}(0.533,0.38,0.263)      RGB{U8}(0.714,0.239,0.435)  RGB{U8}(0.573,0.341,0.494)
 RGB{U8}(0.239,0.753,0.196)  RGB{U8}(0.322,0.42,0.384)      RGB{U8}(0.659,0.576,0.051)  RGB{U8}(0.094,0.18,0.016) 

In the future, most algorithms that want to treat color-as-color will use a Color type, and in the new images there are good tools for "virtually" interpreting even an m×n×3 arrays as if it's an m×n RGB array: http://juliaimages.github.io/latest/. (That documentation is for the future version of Images, not the current one.)

[fpreiswerk]

I understand. Using RGB arrays clearly seems more Julian. That new documentation looks encouraging already. Looking forward to the next version, thank you for all the work.

[timholy]

Obviated by the new Images, see also #585.