Figure 5

DCT coefficient histograms for SDJPEG and SSJPEG patches from uncompressed 512 × 512 image. (a1 and b1)${\mathit{h}}_{1,3}^{\mathrm{AJ}}\left(\mathit{f}\right)$ and ${\mathit{h}}_{3,1}^{\mathrm{AJ}}\left(\mathit{f}\right)$ with QF₁ = 60. (a2 and b2)${\mathit{h}}_{1,3}^{\mathrm{SD}}\left(\mathit{f}\right)$ and ${\mathit{h}}_{3,1}^{\mathrm{SD}}\left(\mathit{f}\right)$ with QF₂ = 90 and (x_S, y_S) = (4,4). (a3 and b3) Normalized distribution of the shifted double quantization error ${\mathit{E}}_{1,3}^{\mathrm{SJR}}$ and ${\mathit{E}}_{3,1}^{\mathrm{SJR}}$. (c1) The original image patch. (c2 and c3) The (1,3)th and (3,1)th DCT coefficient histograms of the SSJPEG-compressed image with QF = 90 and (x_S, y_S) = (4,4), respectively.