corrupt images after copy

What do you mean with 'during a copy'. What are you trying to do excactly?

I apologize for the short description.

What I meant was a copy-operation in war-goals, ear-goals and jar goals.

When executing, for example, a 'maven war', and files are copied to the target directory before packaging the result is similar to the attached files.

This problem is often due to the usage of a filter during the copy of binaries.
We'll try to see if there is a bad setting in a copy task.

If that is the case, is there some way to work around this?

It seems to be a bug.
I don't know when it was introduced.
In the plugin code, for the goal war:war-resources, we have :

    <j:if test="${webSourcesPresent == 'true'}">
      <ant:copy todir="${maven.war.webapp.dir}" filtering="on"
                preservelastmodified="true"
                overwrite="${maven.war.resources.overwrite}">
        <ant:fileset dir="${maven.war.src}"
          includes="${maven.war.src.includes}"
          excludes="${maven.war.src.excludes}">
        </ant:fileset>
        <j:if test="${maven.war.property.expansion}" >
          <ant:filterchain>
            <ant:expandproperties/>
          </ant:filterchain>
        </j:if>
      </ant:copy>
    </j:if>

The filtering is activated but if you exclude your images using maven.war.src.excludes, these ones will not be copied.
Temporarly, what you can do it's to define your binary resources in maven.war.src.exclude.
For example : maven.war.src.exclude=*/.gif,*/.jpg
Then you add a post goal of war:war-resources in you project to copy your binary resources without filter :

<postGoal name="war:war-resources">
    <j:if test="${webSourcesPresent == 'true'}">
      <ant:copy todir="${maven.war.webapp.dir}" filtering="off"
                preservelastmodified="true"
                overwrite="${maven.war.resources.overwrite}">
        <ant:fileset dir="${maven.war.src}"
          includes="${maven.war.src.excludes}"
          excludes="${maven.war.src.includes}">
        </ant:fileset>
        <j:if test="${maven.war.property.expansion}" >
          <ant:filterchain>
            <ant:expandproperties/>
          </ant:filterchain>
        </j:if>
      </ant:copy>
    </j:if>  
</postGoal>

(You noticed that I reversed excludes and includes)
With that it should works.
For us, what we have to do is either to remove the filtering (I don't know if it useful) or to keep it but to add a property maven.war.bin.excludes which will be used to don't copy this resources with a filter.

The filtering in the war plugin was introduced in MPWAR-46. However, the ear and jar plugins don't use the ant:copy task but rather the maven:copyResources tag of the maven jelly tag library. This sems to be an inconsistency unless I'm missing something. You said you also had problems with the ear and jar goals? In this case we'd have to fix this consistently for all plugins, otherwise, I'd say we just revert MPWAR-46.

Our maven.xml contained:

 
<preGoal name="war:init">
   <ant:tstamp>
     <format property="TODAY_LONG" pattern="dd-MM-yyyy" locale="en"/>
   </ant:tstamp>
   <ant:filter token="DATE_FORMAT" value="dd-MM-yyyy" />
   <ant:filter token="BUILD_DATE" value="${TODAY_LONG}" />
</preGoal>

Removing this preGoal fixed the problem.

Wouldn't it be better to be able to enable/disable filtering via a property?

filter="on" is not the only problem. If you activate property expansion, you're stuck if you have binary files to copy.

We can customize the filter property, not sure that this will solve the problem at all. (Still thinking)

Added maven.war.expansion.excludes property to exclude files during a property expansion copy (Fixes corruption of binary files). Applied property expansion to web.xml handling for consistency. Introduced the maven.war.src.filtering property to control whether filtering is enabled or not when copying webapp resources.