Legacy ImageMagick Discussions Archive

Hi,
I am trying to re size the image from 96 DPI to 300 DPI but the conversion is not happening for even long time.
till 180 DPI conversion its worked fine after 180 till 200 i got complete dark image .
Can i know the reason why its taking too long time to convert it to 300 DPI ?

Command line i am using for conversion "convert.exe cardc.jpg -resize 7968x10968 -density 300x300 -quality 50 -compress Group4 -type Bilevel rescale.tiff"

The image with which i am able to reproduce the issue is at https://www.dropbox.com/s/1bqj2qdmuhrm1ok/cardc.jpg

If you remove the options and add then in one by one, you will see that "-density" takes no time at all. The slow process is the compression.

Group 4 compression is already bilevel. Don't also specify "-type bilevel".

The compression is not really the slow part but it is causing it. The slow part is making the image monochrome (color quantization).

Thanks for the correction. "-compress Group4" is slow, but the time is taken by the quantization, not the compression.

EDIT to add:

convert cardc.jpg -resize 7968x10968 -density 300x300 -compress Group4 c.tif
Seconds: 36.69

convert cardc.jpg -resize 7968x10968 -density 300x300 -auto-level -threshold 50% -compress Group4 c2.tif
Seconds: 5.42