The ornamental design for the portable image projector, as shown and described.
FIG. 1 is a perspective view of the portable image projector with the lens cap removed;
FIG. 2 is a bottom perspective view of the portable image projector with the lens cap removed;
FIG. 3 is another perspective view of the portable image projector with the lens cap installed;
FIG. 4 is a side elevational view of the portable image projector of FIG. 1.
FIG. 5 is a front view of the portable image projector of FIG. 1; and,
FIG. 6 is a rear view of the portable image projector of FIG. 1.
The broken line showing the source of images and connecting cord of a portable image projector is included for the purpose of illustrating environmental structure and forms no part of the claimed design.