3 Replies Latest reply on Sep 14, 2011 1:55 AM by Sham_1234

    How Adobe viewer scales images?




      I am putting a JPEG file of lesser resolution than the PDF and is scaling it inside PDF. I have a doubt how the viewer scales the image while rendering? Is it just pixel replication or can we specify inside PDF to use some filters for scaling to get better quality? Can someone please help me regarding this doubt?




        • 1. Re: How Adobe viewer scales images?
          ~graffiti Adobe Community Professional & MVP

          What are you using to create the PDF? If Acrobat, you can go to File>Properties>Initial view to set the scale that it opens at.

          1 person found this helpful
          • 2. Re: How Adobe viewer scales images?
            Sham_1234 Level 1

            Thank you for the reply. Let me make my doubt a bit more clear. I wanted to know how the Adobe viewer scales images, say I put a 100x100 image and while adding in the PDF I give display width and height as 300x300, the PDF viewer scales the image to 300x300. I want to know how the viewer is scaling the image? Just pixel replication or some filtering?




            • 3. Re: How Adobe viewer scales images?
              Sham_1234 Level 1

              I found the answer myself from the PDF standard. Image interpolation is done if the /Interpolate field in the image XObject is set true. I am quoting from the PDF standard below.

              "When the resolution of a source image is significantly lower than that of the output device, each source sample covers many device pixels. As a result, images can appear jaggy or blocky. These visual artifacts can be reduced by applying an image interpolation algorithm during rendering. Instead of painting all pixels covered by a source sample with the same color, image interpolation attempts to produce a smooth transition between adjacent sample values. Image interpolation is enabled by setting the Interpolate entry in the image dictionary to true. It is disabled by default because it may increase the time required to render the image."