;fitsview.pro is a very basic GUI that will display a fits image and allow
;you to change the transfer function (scaling of the image). This is
;so basic because we will adapt this later to display our spectral
;data from the Greenbank telescope.

pro farspec, event

;Get state information
widget_control, event.top, get_uvalue=infoptr
info=*infoptr

xn=float(event.x)/float(info.xsize)
yn=float(event.y)/float(info.ysize)
xn=(xn > 0) < 1
yn=(yn > 0) < 1

xi=fix(xn*info.xpix)
yi=fix(yn*info.ypix)

if (event.press gt 1) then begin
widget_control, event.id,draw_motion_events=1
info.pen=1
endif

if (event.release gt 0) then begin
widget_control,event.id,draw_motion_events=0
info.pen=0
endif

if (info.pen eq 1) then begin

wset, info.winid1
;device, copy=[0,0,xsize=info.xsize*3/4,ysize=info.ysize*3/4,0,0,info.pixwin]
;Re-display the next image
low=info.minpix
high=info.maxpix
q=info.image
q=congrid(q,info.xsize*3/4,info.ysize*3/4, /interp)
tv, bytscl(q,min=(xn*high-yn*high+low),max=(xn*high+yn*high+low)),info.xsize/8,info.ysize/8
;plots,[info.xsize/8,info.xsize*5/8],[info.ysize/8,info.ysize*5/8]
;plot,[0],/nodata,xrange=[-1,1],yrange=[-1,1]
endif

*infoptr=info

end

pro fitsview, image

;Read in the fits file and header.
f=readfits(image,h)
;Create the base widget and name it.
base=widget_base(column=1, title='FITS View', $
tlb_frame_attr=1,/tlb_size_events)
imagebase=widget_base(base, column=1)

;Get the number of pixels in each direction
xsize=fxpar(h,'NAXIS1')
ysize=fxpar(h,'NAXIS2')

;Open a window that has the right aspect ratio for the fits image.
device, get_screen_size=screen_size
draw_xsize=(0.7*screen_size[1])
draw_ysize=((0.7*screen_size[1]*ysize)/xsize)

;Create a draw widget where we can display the image. We also tell it to
;use the program 'farspec' (shown above) when it detects events inside the draw widget.
draw1=widget_draw(imagebase, xsize=draw_xsize, $
ysize=draw_ysize,event_pro='farspec',/button_events,/motion_events)

widget_control, base, /realize
widget_control, base, tlb_get_size=base_size
widget_control, draw1, get_value=winid1

;Tell IDL that we want our draw widget to be the active window where everything will be
;displayed.
wset, winid1
;Get the maximum and minimum pixel in the image for the initial display.
maxpix=max(f)
minpix=min(f)

;Resize the image to fit the inner 3/4 of the draw widget.
q=congrid(f,draw_xsize*3/4,draw_ysize*3/4)
;Display the image with the scale set by the max and min pixels. We also are telling 'tv' to put
;the lower left-hand corner of the image 1/8th of the way up and over (centering it).
tv, bytscl(f,min=minpix,max=maxpix),draw_xsize/8,draw_ysize/8
;Here we are plotting basic axis, not related to the coordinates of the image.
plot,[0],/nodata,xrange=[-1,1],yrange=[-1,1],pos=[0.12,0.12,0.88,0.88]


;Here we are creating a structure that will hold all the information about the current state of
;the GUI. We turn this into a pointer variable that we then store as the user value of the top
;level base widget, just so the procedure 'farspec' get get to it and modify it as we interact
;with the draw widget.
info={winid1:winid1,base_size:base_size,xsize:draw_xsize,xpix:xsize,$
ysize:draw_ysize,ypix:ysize,image:q,arr:f,pen:0,minpix:minpix,maxpix:maxpix}
infoptr=ptr_new(info)
widget_control, base, set_uvalue=infoptr

;Tell the IDL widget manager to start tracking events.
xmanager, 'fitsview', base, /no_block

end