diff --git a/Project.toml b/Project.toml
index e9ef717..3604482 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,6 +3,10 @@ uuid = "d1dcc2e6-806e-11e9-2897-3f99785db2ae"
 authors = ["Mosè Giordano"]
 version = "0.1.0"
 
+[deps]
+FITSIO = "525bcba6-941b-5504-bd06-fd0dc1a4d2eb"
+WCS = "15f3aee2-9e10-537f-b834-a6fb8bdb944d"
+
 [compat]
 julia = "^1.0.0"
 
diff --git a/src/Reproject.jl b/src/Reproject.jl
index 875b927..d2cb43b 100644
--- a/src/Reproject.jl
+++ b/src/Reproject.jl
@@ -1,5 +1,7 @@
 module Reproject
 
-greet() = print("Hello World!")
+using FITSIO, WCS
+
+include("parsers.jl")
 
 end # module
diff --git a/src/parsers.jl b/src/parsers.jl
new file mode 100644
index 0000000..dcc8472
--- /dev/null
+++ b/src/parsers.jl
@@ -0,0 +1,77 @@
+"""
+    parse_input_data(input_data::ImageHDU)
+    parse_input_data(input_data::String, hdu_in)
+    parse_input_data(input_data::FITS, hdu_in)
+
+Parse input data and returns an Array and WCS object.
+
+# Arguments
+- `input_data`: image to reproject which can be name of a FITS file,
+                an ImageHDU or a FITS file. 
+- `hdu_in`: used to set HDU to use when more than one HDU is present. 
+"""
+function parse_input_data(input_data::ImageHDU)
+    return read(input_data), WCS.from_header(read_header(input_data, String))[1]
+end
+
+function parse_input_data(input_data::String, hdu_in)
+    return parse_input_data(FITS(input_data), hdu_in)
+end
+
+function parse_input_data(input_data::FITS, hdu_in)
+    return parse_input_data(input_data[hdu_in])
+end
+
+
+# TODO: extend support for passing FITSHeader when FITSHeader to WCSTransform support is possible.
+
+
+"""
+    parse_output_projection(output_projection::WCSTransform, shape_out)
+    parse_output_projection(output_projection::ImageHDU; shape_out)
+    parse_output_projection(output_projection::String, hdu_number)
+    parse_output_projection(output_projection::FITS, hdu_number)
+
+Parse output projection and returns a WCS object and shape of output.
+
+# Arguments
+- `output_projection`: WCS information about the image to be reprojected which can be 
+                       name of a FITS file, an ImageHDU or WCSTransform.
+- `shape_out`: shape of the output image.
+- `hdu_number`: specifies HDU number when file name is given as input.
+"""
+function parse_output_projection(output_projection::WCSTransform, shape_out)
+    if length(shape_out) == 0
+        throw(DomainError(shape_out, "The shape of the output image should not be an empty tuple"))
+    end
+
+    return output_projection, shape_out
+end
+
+function parse_output_projection(output_projection::ImageHDU, shape_out)
+    wcs_out = WCS.from_header(read_header(output_projection, String))[1]
+    if shape_out === nothing
+        shape_out = size(output_projection)
+    end
+    if length(shape_out) == 0
+        throw(DomainError(shape_out, "The shape of the output image should not be an empty tuple"))
+    end
+    return wcs_out, shape_out
+end
+
+function parse_output_projection(output_projection::String, hdu_number)
+    parse_output_projection(FITS(output_projection), hdu_number)
+end
+
+function parse_output_projection(output_projection::FITS, hdu_number)
+    wcs_out = WCS.from_header(read_header(output_projection[hdu_number], String))[1]
+    
+    if output_projection[hdu_number] isa ImageHDU
+        shape_out = size(output_projection[hdu_number])
+    else    
+        throw(ArgumentError("Given FITS file doesn't have ImageHDU"))
+    end
+    
+    return wcs_out, shape_out
+end
+
diff --git a/test/parsers.jl b/test/parsers.jl
new file mode 100644
index 0000000..73f89ce
--- /dev/null
+++ b/test/parsers.jl
@@ -0,0 +1,97 @@
+using Reproject: parse_input_data, parse_output_projection
+@testset "input parser" begin
+    fname = tempname() * ".fits"
+    f = FITS(fname, "w")
+    inhdr = FITSHeader(["FLTKEY", "INTKEY", "BOOLKEY", "STRKEY", "COMMENT",
+                        "HISTORY"],
+                       [1.0, 1, true, "string value", nothing, nothing],
+                       ["floating point keyword",
+                        "",
+                        "boolean keyword",
+                        "string value",
+                        "this is a comment",
+                        "this is a history"])
+
+    indata = reshape(Float32[1:100;], 5, 20)
+    write(f, indata; header=inhdr)
+    
+    @testset "ImageHDU type" begin
+        result = parse_input_data(f[1])
+        @test result[1] isa Array
+        @test result[2] isa WCSTransform
+    end
+    
+    @testset "Single HDU FITS file" begin
+        result = parse_input_data(f, 1)
+        @test result[1] isa Array
+        @test result[2] isa WCSTransform
+    end
+    close(f)
+    
+    @testset "String filename input" begin
+        result = parse_input_data(fname, 1)
+        @test result[1] isa Array
+        @test result[2] isa WCSTransform
+    end
+    
+    f = FITS(fname, "w")
+    write(f, indata; header=inhdr)
+    write(f, indata; header=inhdr)
+    
+    @testset "Multiple HDU FITS file" begin
+        result = parse_input_data(f, 2)
+        @test result[1] isa Array
+        @test result[2] isa WCSTransform
+
+        close(f)
+        result = parse_input_data(fname, 1)
+        @test result[1] isa Array
+        @test result[2] isa WCSTransform
+    end   
+end
+
+@testset "output parser" begin
+    fname = tempname() * ".fits"
+    f = FITS(fname, "w")
+    inhdr = FITSHeader(["FLTKEY", "INTKEY", "BOOLKEY", "STRKEY", "COMMENT",
+                        "HISTORY"],
+                       [1.0, 1, true, "string value", nothing, nothing],
+                       ["floating point keyword",
+                        "",
+                        "boolean keyword",
+                        "string value",
+                        "this is a comment",
+                        "this is a history"])
+
+    indata = reshape(Float32[1:100;], 5, 20)
+    write(f, indata; header=inhdr)
+    
+    @testset "ImageHDU type" begin
+        result = parse_output_projection(f[1], (12,12))
+        @test result[1] isa WCSTransform
+        @test result[2] isa Tuple
+        @test_throws DomainError parse_output_projection(f[1], ())
+    end
+    close(f)
+    
+    @testset "String filename" begin
+        result = parse_output_projection(fname, 1)
+        @test result[1] isa WCSTransform
+        @test result[2] isa Tuple
+    end
+    
+    wcs = WCSTransform(2;
+                          cdelt = [-0.066667, 0.066667],
+                          ctype = ["RA---AIR", "DEC--AIR"],
+                          crpix = [-234.75, 8.3393],
+                          crval = [0., -90],
+                          pv    = [(2, 1, 45.0)])
+    
+    @testset "WCSTransform input" begin
+        result = parse_output_projection(wcs, (12,12))
+        @test result[1] isa WCSTransform
+        @test result[2] isa Tuple
+        @test_throws DomainError parse_output_projection(wcs, ())
+    end
+end
+
diff --git a/test/runtests.jl b/test/runtests.jl
index 515282e..1809d4d 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,6 +1,7 @@
 using Reproject
 using Test
 using Conda, PyCall
+using FITSIO, WCS
 
 ENV["PYTHON"]=""
 Conda.add_channel("astropy")
@@ -8,5 +9,5 @@ Conda.add("reproject")
 rp = pyimport("reproject")
 
 @testset "Reproject.jl" begin
-    # Write your own tests here.
+    include("parsers.jl")
 end