Questions[convert-command](ubuntu)

According to this question, How can I convert a series of images to a PDF from the command line on linux?, ImageMagick can convert multiple images to a single PDF.

How could I reverse the operation and convert a PDF of several pages to multiple images?

I have tried the following command, but I got the errors shown:

$ convert test.pdf test-%02.png
convert-im6.q16: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408.
convert-im6.q16: no images defined `test-%02.png' @ error/convert.c/ConvertImageCommand/3258.

gs was installed:

$ gs --version
9.26

Ubuntu version:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 19.04
Release:    19.04
Codename:   disco

I have 20 music videos in one folder and I want to change the quality from 1080p to 720p with ffmpeg, because I'm tired of having to convert every single file.
So I want to ask for a solution how to convert a complete folder 1 to 720p quality with destination folder 2?
I previously used this ffmpeg script

ffmpeg -i video1.mp4 -vf scale = 1280:720 -acodec aac -strict -2 output1.mp4
ffmpeg -i video2.mp4 -vf scale = 1280:720 -acodec aac -strict -2 output2.mp4
ffmpeg -i video3.mp4 -vf scale = 1280:720 -acodec aac -strict -2 output3.mp4

up to 20 times

I use ffmpeg on ubuntu 16.04

i have a folder with tons of subfolders containing png's. how can i step recursively through the subfolders and convert that files to pdf?
The pdf should have the name of the subfolder and be saved in the starting folder ... there are no folders in folders, no problem with double names expected. i'm beginner, tried other ideas, but terrible things happend ...

joe

What I want to do is very simple. I've a file.png, which I want to mirror, i.e. the result should be a "reflection" of the original image.

I know big tools like GIMP and InkScape can do that, but I'm hoping for a command-line utility, something like convert (which sadly doesn't seem to have such an option, or at least it's not mentioned in the man page).

I'm trying to make sprite sheets out of animated gifs. The sprites are for my GPS, and each frame needs to be exactly 80x80 pixels.

I used this command:

convert -resize 80x80 input.gif  g.png

which will give you N number of frames of a gif, enumerated like: g-N.png.

What I realized using the power of gimp is that the images have been scaled at some point, which is what I don't want. Shown in the attached picture, is an 80x80px section, where the following sprite over lays the area which is supposed to only be the first sprite.

The very next line in my script is:

convert +append g-*.png $outputFile

which may have a roll in this... I'm not sure.

Complete script source-code:

#!/bin/bash
#set -vx
# Takes an image via an argument, converts it to the sprite style my gps takes.
# PNG image must be exactly 2880x150 or 2881x160 pixels in size. individual sprites, ar 80x80 px
mkdir -p test2
rm test2/*.png 

n=`identify -format "%n\n" $1 | head -1`
m=`expr $n / 2`
outputFile=out`date +%s`.png
#outputFile=out.png
echo  "N: " + $n
echo  "M: " + $m

convert -resize 80x80 $1  test2/g.png
convert +append test2/g-*.png $outputFile
#convert -resize 2880x150 $outputFile
#montage test2/g-$m.png $outputFile