Having drawn a subject, such as a human face, on a piece of paper,
enclose it in a square, as A, B, C, D (Fig. 130), and divide it into
smaller squares by marking off equal parts of the sides and drawing
straight lines across, as when you wish to make a reduced copy of a
picture.
[Illustration: Fig. 132.]
Describe a parallelogram, E, B, F, G, the short side, E, G, being
divided into as many equal parts as A B, in our example 7. From the
centre of the side, B F, draw straight lines to the points of division
on the side E G. Assume the point I, on the side B F, as the height of
the eye above the picture; draw from I to the point E the straight line,
which cuts the lines diverging from H at the points 1, 2, 3, 4, 5, 6, 7.
Through these intersecting points draw parallel straight lines to divide
the triangle into as many trapeziums as there are small squares in the
square A, B, C, D.
Now fill up all the cells of the triangle with corresponding parts of
the drawing, taking the base of the triangle to be the head of the
picture transferred, and the comical distortion will be made. To see it,
however, like its original, bore a hole, K, in a board, L, placed
upright in H, so that the height, L K, equals H I, which must not be
great, in order that the distortion may be remarkable.
Several lines of letters forming a phrase or sentence, can be distorted
in a similar manner, so as to be read only by holding the paper so
inscribed at a certain position as regards the eye. Further anamorphoses
may be made by painting on curved surfaces, cylindrical, conical, or
spherical, which appear natural when seen from a certain point of view.
Still another way is to look at the reflection on a cylindrical mirror
of a drawing made only so to appear regular.
Another way to obtain the distorted picture is to prick out the outlines
of the original drawing, and hold it at an angle to a sheet of paper, so
that the light on the other side, streaming through the pinholes, shall
form a figure, which you can trace with pencil, more or less out of the
true position. To see this changed picture corrected, you must place
your eye where the light was.
By varying such pictures, they can be adapted to being seen aright by
reflections in cylindrical, conical, pyramidal, and prismatic mirrors.