Fix wallhack cameras (#2093)

changes:

Fixed cameras' visibility calculations.
Possibly made cameras slightly faster.

code/_helpers/icons.dm

@@ -886,10 +886,16 @@ proc/generate_image(var/tx as num, var/ty as num, var/tz as num, var/range as nu
 				//Capture includes non-existan turfs
 				if(!suppress_errors)
 					return
+
+	return generate_image_from_turfs(turfstocapture, range, cap_mode, user, lighting)
+	
+/proc/generate_image_from_turfs(turf/topleft, list/turf/turfstocapture, range as num, cap_mode = CAPTURE_MODE_PARTIAL, mob/living/user, lighting = TRUE)
+	var/tx = topleft.x
+	var/ty = topleft.y
 	//Lines below determine what objects will be rendered
 	var/list/atoms = list()
 	for(var/turf/T in turfstocapture)
-		atoms.Add(T)
+		atoms += T
 		for(var/atom/A in T)
 			if(istype(A, /atom/movable/lighting_overlay)) //Special case for lighting
 				continue
@@ -899,7 +905,7 @@ proc/generate_image(var/tx as num, var/ty as num, var/tz as num, var/range as nu
 
 			atoms += A
 
-	//Lines below actually render all colected data
+	//Lines below actually render all collected data
 	atoms = sort_atoms_by_layer(atoms)
 	var/icon/cap = icon('icons/effects/96x96.dmi', "")
 	cap.Scale(range*32, range*32)

code/modules/paperwork/photography.dm

@@ -204,22 +204,29 @@ var/global/photo_count = 0
 	return TRUE	// DVIEW will do sanity checks, we've got no special checks.
 
 /obj/item/device/camera/proc/captureimage(atom/target, mob/living/user, flag)
+	var/obj/item/weapon/photo/p = createpicture(target, user, flag)
+	printpicture(user, p)
+
+/obj/item/device/camera/proc/createpicture(atom/target, mob/living/user, flag)
 	var/mobs = ""
+	var/list/turfs = list()
 
 	FOR_DVIEW(var/turf/T, size, target, INVISIBILITY_LIGHTING)
 		if (user.can_capture_turf(T))
 			mobs += get_mobs(T)
+			turfs += T
 
 	END_FOR_DVIEW
 
-	var/obj/item/weapon/photo/p = createpicture(target, user, mobs, flag)
-	printpicture(user, p)
-
-/obj/item/device/camera/proc/createpicture(atom/target, mob/user, mobs, flag)
 	var/x_c = target.x - (size-1)/2
 	var/y_c = target.y - (size-1)/2
 	var/z_c	= target.z
-	var/icon/photoimage = generate_image(x_c, y_c, z_c, size, CAPTURE_MODE_REGULAR, user)
+
+	var/turf/topleft = locate(x_c, y_c, z_c)
+	if (!topleft)
+		return null
+
+	var/icon/photoimage = generate_image_from_turfs(topleft, turfs, size, CAPTURE_MODE_REGULAR, user)
 
 	var/icon/small_img = icon(photoimage)
 	var/icon/tiny_img = icon(photoimage)