files= FileNames["blackboard.jpg",NotebookDirectory[]];

pix = Import/@files;

Rasterize[img1 = pix[[1]]]

img1pixel = ImageData[img1];

img11 = Image[1-img1pixel]; (*This part is to create a show image*)

Rasterize[t= ImageConvolve[img11, {{0,2,0},{1,3,1},{-2,-9,-1}}]]

Sharpen[t,8] // Rasterize

Rasterize[1-Sharpen[t,8]]