Well, thanks for that. But, sadly, it leaves me no clearer than before; I'll just have to play around, unless anyone else has experience of using this function.
Angela -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Dermot Paikkos Sent: 09 June 2006 14:37 To: [email protected] Subject: RE: [magick-users] Problems Resizing Gifs with a colour depth of 16 There is a map function but I have no experience of this method. from the docs: "choose a particular set of colors from this image. [convert or mogrify]. By default, color reduction chooses an optimal set of colors that best represent the original image. Alternatively, you can choose a particular set of colors from an image file with this option. Use +map to reduce all images in the image sequence that follows to a single optimal set of colors that best represent all the images. The sequence of images is terminated by the appearance of any option. If the +map option appears after all of the input images, all images are mapped." Dp. On 9 Jun 2006 at 13:00, Angela Slaney wrote: > > Yes they do, but then the image file size triples to around three > times the original. So after I've scaled, (I do use scale) I do a > Quantize back to 16 colours; it is then the problems occur. The 16 > colours chosen are not those in the original colour map. Is there a > way around this? > > Angela > > -----Original Message----- > From: Dermot Paikkos [mailto:[EMAIL PROTECTED] > Sent: 09 June 2006 10:50 > To: Angela Slaney; [email protected] > Subject: Re: [magick-users] Problems Resizing Gifs with a colour depth > of 16 > > I am not entirely sure I am that I am doing what you want but if I use > -scale 480x480 the colours appear okay to me. I suspect that is what a > browser is doing when it scales a image. > > "-scale uses a simpler, faster algorithm, and it ignores the -filter > selection" > > there is a perlmagick scale method too. > > HTH. > Dp. > > > On 9 Jun 2006 at 10:19, Angela Slaney wrote: > > > Hi, > > > > I'm using PerlMagick version 6.2.8 on my server. > > > > I'm grabbing non-copyright wind-speed analysis images with a colour > > depth of 16. An example original image is here at > > http://activitae.com/images/wind.gif > > > > I need to reduce the image in physical size and, hopefully, byte > > size too to display on smartphones or PDAs. > > > > When I grab an image and try to keep the colour depth the same I end > > up with an image with grubby brown colours whereas they were yellow, > > orange and red. Example http://activitae.com/images/wind1.gif > > > > > > I've read the archive's previous posts about the file size of gif > > images ending up larger than they started because of artifacts added > > during resizing. And this certainly happens with these reduced > > colour depth images, although I have had good results using > > perlMagick to resize other web images. But these end up being 12Kb > > larger than the original despite being reduced to 71%. > > > > The problem seems to be that Resize and Sharpen return the image to > > a 256 colour depth. And then a Quantize back to 16 seems to choose > > any colours in the image. > > > > My question is this is there a way to restrict the Resize and > > Sharpen functions to only use the original image's colour table so I > > end up with an image with correct colours and of smaller file size? > > > > And second question. If I handle an image request by passing back a > > web page with <img src="http://...."; height='483' width='483' > the > > browser then does the work of image reduction but appears to do it > > far better than PerlMagick does. Example is here > > http://activitae.com/NApda-2.htm . Is someone able to explain to me > > why? > > > > All help appreciated. > > > > Angela > > > > > > _______________________________________________ > > Magick-users mailing list > > [email protected] > > http://studio.imagemagick.org/mailman/listinfo/magick-users > > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.394 / Virus Database: 268.8.3/359 - Release Date: > 08/06/2006 > > > > _______________________________________________ > Magick-users mailing list > [email protected] > http://studio.imagemagick.org/mailman/listinfo/magick-users _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.8.3/359 - Release Date: 08/06/2006 _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
