Author Topic: Repairing rotated images  (Read 263 times)


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Repairing rotated images
« on: June 26, 2022, 02:00:53 am »
    Some big things are going on in the Forum, judging by some recent posts. Wowser.
    This post is more modest but we nonetheless wanted to report that the Lazarus picture and video editing program VirtualU has several new tools that repair rotated/unrotated picture and video images.
    When an image is rotated to a perpendicular angle like 90, 180 and 270 degrees then no changes are made other than the rotation.
    However, if an image is rotated to a non-perpendicular angle like 45 degrees etc. then the image will sometimes suffer quality loss, depending upon the gradients, variety and number of colors that are involved.
    This quality loss involves ragged internal and external edges, incorrect pixel colors and sometimes an undesired and noticeable "shearing" effect which looks like adjoining rows and columns of pixels that appear to slide in opposite directions.
    The new button tools on the rotation page titled Clean Edges and Clean Interior will in most cases remove such imperfections incurred after rotations involving non-perpendicular angles. The Clean Interior button handles edge softened foreground images and the user can adjust the amount of change made to the image.
    Even with cleaning, not all images look good after custom rotations but these tools ensure that most images can be rotated to any angle with no discernable quality loss. The program does this by slightly diffusing or softening images.
    The attached example flower2.gif illustrates what these tools do. Fig. 1 shows a flower before rotation. This image has interior edge softening but raster scan edges. Fig. 2 shows the flower after it has been rotated 45 degrees clockwise. The exterior and interior edges of the petals are jagged with messed up pixels. Fig. 3 shows the rotated flower after the tools Clean Edges and Clean Interior have been used. The entire image has been improved from Fig. 2. Fig. 4 shows the image after edge softening has been applied.
    The attached file group2.gif shows how these tools can be used on images that have not been rotated. Fig. 5 and Fig. 7 show images that have some individual pixels which are too bright. This often happens with animated GIFs. Fig. 6 and Fig. 8 show the images after treatment with the Clean Interior button.
    Other changes have also been made to VirtualU. When VirtualU is run for the first time then the program runs a settings test in which the main working page moves to the left and upward before returning to its original position. The program now runs this test only once and never again thanks to some new code that records and uses the monitor serial number.
    VirtualU may be downloaded from OpenDrive cloud storage at the address below.
    Thank you Lazarus and best regards.

    VirtualU program files are contained in
    download link:

    Instructions, developmental log reports and examples
    readme.rtf download link:


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