c++ - How to set opacity to png image with transparent background using Magick++ -

-

i'm using imagemagick render images. open png file magick::image , draw on magick::image , set opacity png image. , save jpg file.

in saved file transparent background becomes black.

example code: 

    image newimage;     newimage.size(geometry(1000, 1000));     newimage.fillcolor(color(50, transparentopacity / 2, 50));     newimage.draw(drawablerectangle(0, 0, 1000, 1000));      image originalimage("test-image-1.png");     originalimage.opacity(transparentopacity / 2);     newimage.composite( originalimage, 300, 100, atopcompositeop );      newimage.magick("jpg");     newimage.write("testimage3.jpg");

is possible set transparency 50% image , full transparent background?

the issue line:

originalimage.opacity(transparentopacity / 2);

the source, "test-image-1.png", has alpha-channel looks like...

orignal alpha channel

when set opacity 50%, you're setting whole channel, not reducing level 50%. alpha-channel altered originalimage.opacity looks looks this...

50% alpha-channel

there many ways alter alpha-channel reduce image opacity. pixel iteration, fx, , level color name few. i'm fan of isolating alpha channel, altering levels, , coping channel image. example below "swaps" color values 50% opacity == gray50.

image originalimage("test-image-1.png"); image mask(originalimage); // clone image mask.channel(opacitychannel); // isolate alpha-channel /*   example i'll mimic cli options:   "-fuzz 50% -fill gray50 -opaque black" */ mask.colorfuzz(maxrgb * 0.5); mask.opaque(color("black"), color("gray50")); mask.negate(); // copy mask image new alpha-channel originalimage.composite( mask, 0, 0, copyopacitycompositeop );

reduced opacity 50%

now can composite on image without worry of black background.


Comments

Post a Comment

Popular posts from this blog

Java 3D LWJGL collision -

-
i making 3d java game lwjgl library, , wondering how add collision detection, player not go through models. i using obj models. here objloader class, loads models: package renderengine; import java.io.bufferedreader; import java.io.file; import java.io.filenotfoundexception; import java.io.filereader; import java.util.arraylist; import java.util.list; import models.rawmodel; import org.lwjgl.util.vector.vector2f; import org.lwjgl.util.vector.vector3f; public class objloader { public static rawmodel loadobjmodel(string filename, loader loader){ filereader fr = null; try { fr = new filereader(new file("res/"+filename+".obj")); } catch (filenotfoundexception e) { system.err.println("couldn't load file!"); e.printstacktrace(); } bufferedreader reader = new bufferedreader(fr); string line; list<vector3f> vertices = new arraylist<vector3f...
Read more

spring - SubProtocolWebSocketHandler - No handlers -

-
i have ugly error during deploying spring app on jboss. 18:11:16,025 error [org.apache.catalina.core.containerbase.[jboss.web].[default-host].[/consumer]] (msc service thread 1-7) exception sending context initialized event listener instance of class org.springframework.web.context.contextloaderlistener: org.springframework.context.applicationcontextexception: failed start bean 'subprotocolwebsockethandler'; nested exception java.lang.illegalargumentexception: no handlers @ org.springframework.context.support.defaultlifecycleprocessor.dostart(defaultlifecycleprocessor.java:176) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.springframework.context.support.defaultlifecycleprocessor.access$200(defaultlifecycleprocessor.java:51) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.springframework.context.support.defaultlifecycleprocessor$lifecyclegroup.start(defaultlifecycleprocessor.java:346) [spring-context-4.1.3.release.jar:4.1.3.release] @ org.s...
Read more

methods - python can't use function in submodule -

-
my folder structure this: pythonstuff/ program.py modulea/ __init__.py foo.py bar.py here's code bar.py : def hello(): print("hello, world!") here's code program.py : #!/usr/bin/env python3 modulea import bar bar.hello() i run $ python3 program.py somehow error: file "program.py", line 3, in <module> bar.hello() attributeerror: 'module' object has no attribute 'hello' edit: __init__.py file empty. edit2: after trying realized had bar.py in root directory contained hello() method. bar.py in modulea/ directory empty. add it import os __all__ = [] module in os.listdir(os.path.dirname(__file__)): if module != '__init__.py' , module[-3:] == '.py': __all__.append(module[:-3]) the init .py files required make python treat directories containing packages; done prevent directories common name, such string, unintentionally hiding v...
Read more