How to get jpg dimensions in Cobol

I figured it out.

This works:

      SELECT jpgFile ASSIGN TO INPUT-OUTPUT jpg-file-name

              ORGANIZATION IS BINARY SEQUENTIAL.

      DATA DIVISION.

      FILE SECTION.

      fd  jpgFile.

      01  jpgFile-REC pic x.

      WORKING-STORAGE SECTION.

     * Start of Frame 0 line

      01 SOF0       pic xx value x"FFC0".

      01 SOF0-line.

        03 SOF0-Len   pic xx.

        03 bit-depth  pic x.

        03 jpg-height pic xx.

        03 jpg-width  pic xx.

      01 test-bytes.

        03  last-byte  pic x.

        03  cur-byte   pic x.

      01 hex-in-byte   pic x.

      01 dec-out       pic 9(3).

      01 dec-pos1   pic 9(3).

      01 dec-pos2   pic 9(3).

      01 my-hex.

        03  my-hex1  pic x.

        03  my-hex2  pic x.

      01 ws-image-dim  pic 9(5).

      01 image-height  pic 9(5).

      01 image-width   pic 9(5).

      LINKAGE SECTION.

      77  L-JPG-FILE-NAME  PIC X(250).

      77  L-IMAGE-HEIGHT   PIC 9(5).

      77  L-IMAGE-WIDTH    PIC 9(5).

      PROCEDURE DIVISION USING L-JPG-FILE-NAME, L-IMAGE-HEIGHT,

                                                L-IMAGE-WIDTH.                        

      1-MAIN-LOGIC.

          move L-JPG-FILE-NAME to jpg-file-name.

          perform READ-IMAGE-FILE

          move image-height to L-IMAGE-HEIGHT.

          move image-width to L-IMAGE-WIDTH.

          exit program.

          stop run.

      READ-IMAGE-FILE.

          OPEN INPUT jpgFile.

          MOVE "N" TO EOF.

          move x"01" to last-byte

          perform until eof = "Y"

             READ jpgFile AT END MOVE "Y" TO EOF

             end-read

             IF EOF = "N"

                move jpgFile-REC to cur-byte

                if test-bytes = SOF0

                   perform PROCESS-SOF0-LINE

                   move "Y" to eof

                else

                   move cur-byte to last-byte

                end-if

             end-if

          end-perform.

          close jpgFile.

      PROCESS-SOF0-LINE.

     * read the next 7 bytes into the SOF0-line to get the height and width.

          move 1 to sub

          perform 7 times

             READ jpgFile AT END MOVE "Y" TO EOF

             end-read

             IF EOF = "N"

                move jpgFile-REC to SOF0-line(sub:1)

             end-if

             add 1 to sub

          end-perform

          move jpg-height to my-hex.

          perform CALC-DIM.

          move ws-image-dim to image-height.

          move jpg-width to my-hex.

          perform CALC-DIM.

          move ws-image-dim to image-width.

      CALC-DIM.

          move my-hex1 to hex-in-byte

          perform hex2dec.

          move dec-out to dec-pos1

          move my-hex2 to hex-in-byte

          perform hex2dec.

          move dec-out to dec-pos2

          multiply dec-pos1 by 256 giving ws-image-dim

          add dec-pos2 to ws-image-dim giving ws-image-dim.

      HEX2DEC.

          EVALUATE hex-in-byte

             WHEN X"00" MOVE 000 TO dec-out

             WHEN X"01" MOVE 001 TO dec-out

             WHEN X"02" MOVE 002 TO dec-out

             WHEN X"03" MOVE 003 TO dec-out

             WHEN X"04" MOVE 004 TO dec-out

             etc, etc through x"FF"

haha, thanks for posting the solution here, it helps me solve the image dimension issue.

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tags: image programming    image width & height