Fig. 1. Flow of the proposed interpolation algorithm for Raman imaging

Fig. 2. Interpolation strategy of VFI

Fig. 3. The principle of Voigt function fitting interpolation points with adjacent points in Mode 1
(a): Voigt function of point 1; (b): Voigt function of point 3; (c): Voigt function of point 2

Fig. 4. Experimental comparison image of tablet 1 and cell 1 in mode 1
(a): The image to be interpolated of tablet 1 (The spatial resolution is 19×105); (b): The image after interpolating one row in (a) (37×105); (c): The contrast image was collected with the same spatial resolution as (b) (37×105); (d): The image to be interpolated of cell 1 (The spatial resolution is 19×189); (e): The image after interpolating one row in (d) (37×189); (f): The contrast image was collected with the same spatial resolution as (e) (37×189)

Fig. 5. Experimental comparison image of tablet 1 and cell 1 in mode 2(a): The image to be interpolated of tablet 1 (The spatial resolution is 19×53); (b): The image after interpolating one point in (a) (37×105); (c): The contrast image was collected with the same spatial resolution as (b) (37×105); (d): The image to be interpolated of cell 1 (19×95); (e): The image after interpolating one point in (d) (37×189); (f): The contrast image was collected with the same spatial resolution as (e) (37×189)

Fig. 6. Compound histogram of interpolated one line/one point Raman image and same spatial resolution contrast Raman image of tablet 1 and cell 1 in two modes
(a): Compound histogram of tablet 1 in mode 1; (b): Compound histogram of cell 1 in mode 1; (c): Compound histogram of tablet 1 in mode 2; (d): Compound histogram of cell 1 in mode 2

Fig. 7. Raman images of tablet 1 and cell 1 interpolated by VFI with different number of interpolations in mode 1
(a): Table 1 interpolates 3 lines of Raman image (145×105); (b): Table 1 interpolates 7 lines of Raman image (289×105); (c): Cell 1 interpolates 3 lines of Raman image (145×189); (d): Cell 1 interpolates 7 lines of Raman image (289×189)

Fig. 8. Raman images of tablet 1 and cell 1 at different scanning intervals and after interpolation in mode 1
(a): Raman image of tablet 1 (The spatial resolution is 9×105); (b): Raman image of tablet 1(5×105); (c): Raman image of cell 1(9×189); (d): Raman image of cell 1(5×189);(e): Interpolated Raman image of tablet 1 (37×105); (f): Interpolated Raman image of tablet 1 (37×105);(g): Interpolated Raman image of cell 1(37×189); (h): Interpolated Raman image of cell 1(37×189)

Fig. 9. Diagram of component information loss
(a): Raman image of cell 1 (The spatial resolution is 37×105); (b) Raman image of cell 1(19×105); (c): Interpolated Raman image of (b)

Table 1. Histogram Euclidean distances and SSIM values for the two samples