Legacy ImageMagick Discussions Archive

about fraction cropping, i see.

i have to report my fault, only running "convert -size 800x600 xc:'#00000000' result.png" will produce 2-bit png, if adding "png32:" will produce normal png.

and another question, how can i use xc(with hex) to create 8-bit png?

1)
use [src] -gravity center -crop 100x100+0+0 +repage [dst]

to get exactly 100x100. Using percent is not recommened as you will not get exactly the size you want.


2) you have to put hex colors in quotes

convert -size 800x600 xc:"#00000000" png32:result.png
or
convert -size 800x600 xc ...

here i have a image whose size is 300x300, i want to get little 100x100 images?

how can i use crop parameter to support fraction cropping?

convert -crop 33.333333...%x33.333333...% [src] [dst]

??????

the second question is about xc?

formly, i always use 'convert -size 800x600 xc:#00000000 png32 ...

composite [overlay] [background] [result]

you lost [result] and [overlay] [background] position is wrong

I am not familiar with -mask. To composite with a mask the command syntax is:

convert backgroundimage overlayimage maskimage -compose somecomposemethod -composite resultimage

see -compose methods at http://www.imagemagick.org/Usage/compose/

To create an image of a specific size and color ...

see http://www.imagemagick.org/Usage/compose/#compose

it allows the mask to control where two images are composited over each other or using other -compose settings

does cmd like this?
convert [overlay] [background] -mask [mask] [result]
i find strange result, only get [overlay] and ...

i found its explanation - Composite the image pixels as defined by the mask.

what's the meaning? filter a image according to a specified mask?

regards

daer fmw42, thx for your reply

but point of my question is that i want any background

your method is suitable for background created by myself or manipulated by IM
in my requirement, background should be freewill, from real photo or computer graphics, not only described by IM

in fact, i try use ...

here i have a icon in a green background without alpha and another background

i want to do a color blending to produce the icon in the background

like this:
a icon in a green background(no alpha)
http://i16.photobucket.com/albums/b30/haibarapcicp/green.jpg

another white background(in fact i ...

i want a null image, it means rgba be all zero(?)

convert -size heightxwidth -background none {result}?

it seems wrong and infos me lacking of source

what should i do?

regards