Timg

Command line: Timg

Description: transform (correlate) images

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Menu: TopoLT » Images » Transform images

Using this commands you can realize transformation (correlations) of raster images from drawing in order to be put in coordinates system.

Selecting one or more points with correspondent between image and drawing coordinates system can do images transformation. Transformation points are saved in a file and in case when for an image transformation is forgotten, applying once again command Timg you will be notified there are untransformed images and you will be requested to confirm deleting, adding or processing these images.

Rotated images are accepted for transformation. In this way, for images that have to be brought into a rotated coordination system, you can rotate the image so that to be parallel to this system after which you can make the transformation.

There are not accepted deformed images (images with deformations on angles or aspect deformations) or flipped images. These images are returned to the form without deformations and without flipping. Change is signalized through a warning message. If you want to flip image use command ChImg.

Transformation can be made in the following ways:

· move points inside image;

· affine and move points;

· affine;

· projective;

· polynomial conform second degree;

· polynomial second degree with 5 terms.

At the same time with transformation you can do the following images changes:

- images can be saved in one of the following formats: .bmp, .jpg, .pcx, .png, .tga, .tif (color tif files are not saved with compression LZW that is why we recommend you to use Windows programs to compress them);

- color format can be changed from Black&White to True color (32bit), change from a lower color format to a better one won’t be made because is senseless;

- images can be cut in order to keep only the interest part from image, cut can be made on the limit given by minimum and maximum constraining points or outside this limit with a distance (in case you want to keep from a map informations about graticule, map name, etc.). Cut is useful to eliminate from raster image parts that don’t present interest, achieving in this way a smaller file and an increase of processing speed when loading image in drawing;

- images can be framed (Clip) on constraining points. Framing is useful to visualize from an image only the part with map, exterior part being hidden. Framing can be made on maximum border of constraining points (points through which you get the greatest area), points on borders (the nearest points from the image border) or on corners (through 4 best positioned points from corners);

- after transformation points can be made unselectable (ImageFrame = Off) to avoid accidental selecting.

Using command Uimg can do return to previous images.

Initial images are saved in files with extension .bk1, .bk2, etc. when they are modified. Files with extension .bk1, .bk2, etc. are used for returning to initial images using command Uimg. Deleting these file will be done manually only after images transformation process ends.

Equations form:

1. for affine transformation

X = a0 + a1*x + a2*y

Y = b0 + b1*x + b2*y

2. for projective transformation

X = (a1*x + b1*y + c1) / (d1*x + d2*y + 1)

Y = (a2*x + b2*y + c2) / (d1*x + d2*y + 1)

3. for polynomial transformation conform second degree

X = a0 + a1*x + a2*(x²-y²) - b1*y - 2*b2*x*y

Y = b0 + b1*x + b2*(x²-y²) + a1*y + 2*a2*x*y

4. for polynomial transformation of second degree with 5 terms

X = a0 + a1*x + a2*y + a3*x*y + a4*x²

Y = b0 + b1*x + b2*y + b3*x*y + b4*x²