The Dog Show

FullSizeRenderOK here is my question. The pen and ink sketch was drawn on white paper. I took a photograph of it with my cell phone, cropped the picture so it had clean straight edges then, moved it over to my blog. Now, the white paper looks grey. Because I post photographs of paintings with color, I don’t want to have a colored background on my main blog page. I don’t want black either. How do I get a black or colored mat or background for the drawing so the drawing shows black ink on white paper?