Фото: Алексей Майшев / РИА Новости
公式： f(x)={xif x0α(ex−1)if x≤0
。搜狗输入法下载对此有专业解读
圖像來源，Getty Images
SSIM (Structural Similarity Index Measure) compares two images by evaluating luminance, contrast, and structural patterns across local windows. It returns a score from -1 to 1: 1.0 means the images are pixel-identical, 0 means no structural correlation, and negative values mean the images are anti-correlated (less alike than random noise). For glyph comparison, it answers the question: do these two rendered characters share the same visual structure?