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Rotating An Image WITHOUT Losing Any Details

Discussion in 'General GIMP help' started by dsvendse, Jan 25, 2013.

  1. dsvendse

    dsvendse New Member

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    Rotating An Image Using GIMP 2.8.0. WITHOUT Losing Any Of The Image:

    *** Rotating an image in GIMP is quite simple. What I had trouble finding on-line help with, was how to Rotate an image without losing any of it's corners or other details! Here is the quick and easy solution that I came up with after several hours of trying, and one that will leave you with the complete, original image (No Cropping...no loss of image details).

    Read and follow these steps carefully, and what worked for me, will work for You!


    1. Open the image file into GIMP.
    2. Zoom Out until the image height appears to be about one-third of your work space.
    *Clicking on the 'minus' key ( - ) of your keyboard is the fastest way to do this.
    3. Select Image and then Canvas Size from the top, pull-down menus.
    4. In the resulting 'dialog box', just below and to the right of where it says Canvas Size:
    a. Click on the two, small 'chain link' icons.
    b. Click on the little box that has a small, 'down arrow' on it, and select Percent.
    c. Increase the Width and Height to 150%.
    d. Click on the box about halfway down and to the right side of the 'dialog box' that says Center.
    e. Click on Resize.
    5. Select the Rotate Tool from the 'Toolbox-Tool Options' dock.
    6. Click inside the original image.
    7. Rotate the original image from either inside the resulting 'dialog box', OR by clicking/holding and
    dragging the original image to the desired angle.
    8. Click Rotate, and wait for the original image to rotate.
    9. Select Image and then Fit Canvas to Layers from the top, pull-down menus.
    10. Select File and then Export from the top, pull-down menus to complete your project, just as you
    would for any other GIMP 2.8.0.project.

    *** The values given in these steps are NOT 'written in stone'...there's nothing magical about them, but they will give you a place to start from, and do work!

    Have Fun!


    dsvendse
     
  2. ofnuts

    ofnuts Member

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    You don't need to increase the canvas size before the rotation... The rotated layers are not cropped, they are just larger than the canvas, so the previous corners don't show. You can adjust the canvas size after the rotation: "Image/Fit canvas to layers".

    Technically, all rotations make you lose some detail. The pixels in the final image are an interpolation of the original pixels. If you are using the Sinc/Lanczos algorithm for your interpolations the loss is usually negligible on the first rotation (a trained eye will notice it on text).
     
  3. Arzoroc

    Arzoroc Moderator Staff Member

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    Thanks for the contribution dsvendse!
    I'm not too sure this will really give you a lossless transformation though. I don't even think there is such thing as lossless rotation in Gimp or Photoshop.

    Let me show you an example of what I mean:
    This is a 6x6 Pixel background with a "circle" (rather a block on these dimensions but whatever) on it:
    [​IMG]
    If I want to rotate this image by 45 degrees now, I run into a problem: There's pixels that are half-way between some of the pixels in the 5x5 "grid" that the image contains. Gimp now has an algorithm for filling the 5x5 pixels in a way that is closest to the actual image. This is what it did with my image:
    [​IMG]
    Not too good, but good enough for explanation purposes.
    The actual rotated image, however, contains data that is impossible to display in the existing grid, and increasing the canvas size (not scaling up, but increasing), will not fix this issue. It may give different results because the algorithm works differently (thus maybe also decreasing detail loss somehow), but it does not prevent any loss from happening.

    If you do know any backstory about the algorithm or why this gives less errors/better quality, please share them because I'd love to know them ;D
     
  4. dsvendse

    dsvendse New Member

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    THANKS for the Reply!
    The nice folks over at GIMPUsers had the Best solution to my problem.
    I was soooo close to it, but my lack of knowledge and experience with GIMP just wasn't what I needed it to be. :)

    SIMPLE SOLUTION:
    1. ROTATE
    2. IMAGE/FIT CANVAS TO LAYERS
    ***That's all it took!

    The details that I was losing were actual parts of the original image, and the only solutions I could find on-line saw me cropping out bits and pieces of the image. I knew there had to be better and more acceptable methods, and was quite happy with what I came up with on my own, UNTIL I got the help that I was looking for, from folks who knew the program.

    At least now, other folks facing the same problem will have a better chance of locating a quick solution! :)

    Take care!

    dsvendse
     
  5. dsvendse

    dsvendse New Member

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    THANKS for your kind Reply!
    So 'easy, when you know how'... ;)

    Have a GREAT day!

    D.
     
  6. ofnuts

    ofnuts Member

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    You should have known... after the rotation, the dotted line that shows the layer boundary is displayed outside the canvas... this is a hint that the layer is bigger than the canvas... and is still there in full.
     
  7. dsvendse

    dsvendse New Member

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    I do....now! :)

    Thanks again..

    D.
     

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