I obtain rare effect when I scale a image in imagemagick

[diegomage]

I scale this image with this command

convert img -scale 270% imgr


and I obtain this effect in the border




How I could convert i image without lose or change the colors

[fmw42]

try

Code: Select all

convert PaeLa.png -sample 270% result.png

[diegomage]

this works very thankyou

[fmw42]

What is your IM version and platform? I do not get that effect even using your command:

Code: Select all

convert PaeLa.png -scale 270% result.png

Are you sure that is the command you actually used (not -resize nor -resample)

How did you view the result in zoomed view? What viewer? Perhaps your viewer is doing bilinear enlarging rather than pixel replication?

[diegomage]

this is my version
Version: ImageMagick 7.0.6-0 Q16 x86_64 2017-07-12 http://www.imagemagick.org
Copyright: © 1999-2017 ImageMagick Studio LLC

[diegomage]

my command is scale my viewer is kolour paint (but i use a convert command for check the color and the color changed in the border too)

[diegomage]

this is my result image using this command

Code: Select all

convert img -scale 270% imgr

convert img -scale 270% imgr

[fmw42]

Using IM 6.9.6.7 Q16 and IM 7.0.6.7 Q16 HDRI, I get your same result when using -scale when zooming a factor of 8. But using -sample works fine for me in both versions when zooming a factor of 8. Try -sample.

See
http://www.imagemagick.org/script/comma ... php#sample
http://www.imagemagick.org/script/comma ... .php#scale

If you were using an integer enlargement (200%, 300%, 400% etc), then both should produce the same results with no new colors.

I am not sure about non-integer enlargement values, but it was my understanding that both -scale and -sample enlarged with the same method. So if this is correct, then perhaps there is a bug. However, if I am wrong and -scale enlarges by non-integer values by blending, then this result is correct.

[Bonzo]

For your information V7 uses magick rather than convert. If you installed legacy programs convert will work but you will then be using a V6 version.

[magick]

If you scale by whole integers 200, 300, and 400%, for example, no new colors are introduced. The scanlines are duplicated. However if you enlarge by a non-integer factor, new colors are introduced. Scanlines are blended. 270% is a factor of 2.7. So in the example you provide, new colors are expected.