Here is Charles Partee on Imago Dei (image of God) and Imago Christi (image of Christ) in the theology of John Calvin:
Having praised the original creation of human understanding and will, Calvin concludes that God is comprehended in Christ alone (II.6.4) until such time as we shall see God as he is (II.14.3). God cannot be known apart from Christ because “all thinking about God outside Christ is a vast abyss which immediately swallows up all our thoughts.” Those who philosophize about God
without Christ are deluded (compare 1 Pet. 1:20; I John 2:22). Since Calvin’s theology is based on faith, not on reason, the Christian life is not linked by chains of reasoning but guided by faith in Christ, which is the principal work of the Holy Spirit. “We hold ourselves to be united with Christ by the secret power of his Spirit (III.11.5). “Therefore, that joining together of head and members, that indwelling of Christ in our hearts—in short that mystical union—are accorded by us the highest degree of importance, so that Christ, having been made ours makes us sharers with him in the gifts with which he has been endowed” (III.11.10).
Image and Likeness. The same dynamic from created to fallen to restored also applies to Calvin’s view of the image of God. Mankind was originally created in God’s image, which means “that man was blessed, not because of his own good actions, but by participation in God” (II.2.1). The image of God is not to be understood only as a possession but a relationship—and “participation in God” involves “union with Christ.” In the fall, while “God’s image was not totally annihilated and destroyed in [Adam], yet it was so corrupted that whatever remains is frightful deformity” (I.15.4). Human sin means that the image of God cannot be understood solely in terms of creation or fall but in the true image of God restored in Jesus Christ. In other words, Calvin defines the image more in terms of redemption than creation. Regeneration is nothing else than the reformation of the image of God in the godly, but the second creation of the image in the restoration by Christ is a far more rich and powerful grace (Com. Eph. 4:24). The grace of God exhibited in Christ exceeds all miracles. Indeed the redemption that he has brought surpasses even the creation of the world (Com. Is. 9:6).
Since Christ is the perfect image of God and we are united to him, we are restored to God’s image. . . . [Charles Partee, “The Theology of John Calvin,” 86-87]
Rich stuff, and stuff that correlates well with what we might find in the theology of Thomas Torrance, and of course Athanasius. I think bringing TFT, Athanasius, Barth, and others into a discussion with Calvin on imago Dei/Christi could be a fruitful exercise and one that would serve and edify the body of Christ well! Being images of the image of God in Christ is a fantastic reality that at least personally I can’t meditate on enough!