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TheJoe.it Into the (open) source

12Jun/104

Tutorial: Perspective correction (the linee cadenti) with Gimp

Finished work

In this tutorial we deal with correct perspective a photo with Gimp. Often (especially in the narrow streets) having to take pictures of monuments or facades of tall buildings, having available a limited field for framing. It is clear that we will be closer to the monument over the photo will be "far" from axonometrically correct. The perspective correction is also called correction (or modification) the falling lines. This is because taking a picture up close to an architectural one gets the impression that the monument is falling backwards (architectural lines converge upwards.

What we will do today is "straighten" the lines of a facade, Gimp as well as we should have another couple of plugins: "MathMap" and "FX-Foundry".

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MathMap is a plugin for Gimp rather complex. Can also be used as a stand-alone command-line, but of course it is easier to use with Gimp because of the graphics facilities that follow. Unlike MathMap FX-Foundry is a plugin much more primitive. Creates an entry in the main menu and special deals only speed up some operations already feasible with Gimp, but that would cause us to lose time.

We find the filters MathMap below "Filters" - "Generic" - "MathMap", and filters FX-Foundry in its menu (on call to bar menus).

First you take a photo that lends itself to the work. Transform the first photo, and the final result is the following:

Original

Lavoro ultimato

Finished work

The first thing we must do is correct perspective. Let's go over "Filters" - "Generic" - "MathMap" - "Distorts" - "Bilinear interpolation".

Let's go under the tab "User Values" and move the value "a3" trying to verticalize as much as possible the lines.

Now we'll have to cut off le zone "Empty" of the image with the tool "Cutter" .

And now we will give a cut to the next step by adding the authentic vignetting. "FX-Foundry" - "Photo" - "Effects" - "LOMO Effect".

At this point in the tab "Levels" reduce the opacity vignetting of the 50%, so we get the final result.

Lavoro ultimato

This tutorial is for the sole purpose of show how to correct the perspective of a photo, we must not forget, however, that photography is art. If a picture we like it like no one forces us to correct the colors, theexposure o la outlook. It all depends on the outcome we want to achieve.

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I keep this blog as a hobby by 2009. I am passionate about graphic, technology, software Open Source. Among my articles will be easy to find music, and some personal thoughts, but I prefer the direct line of the blog mainly to technology. For more information contact me.

Comments (4) Trackbacks (0)
  1. Oh, are ricapitato on your blog! ๐Ÿ˜€

    Only the GIMP menu has changed since that time :/

  2. for example, I preferred the original own this photo! ๐Ÿ˜€
    but…are views! hihihi ..ciaoooo

  3. I must say that the effect “LOMO” I like! ๐Ÿ˜€

    However, like you said “photography is art” and is an important thing, because sometimes the best photos are those that are not really correct…but I must say that the bits of advice that you gave to the post-production are very interesting. Really Bravo! ๐Ÿ˜‰ mi piaciiii


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