Replace transparency in PNG images with white background

Question

I ve got some PNG images with transparency  and I need to create versions with the image layer composed onto a white background   I ve tried various things with Image Magick  convert  operations  but either nothing happens at all or I get an error   I don t want to go to an intermediate JPG form because I don t want the artifacts   Of course it s easy to do this in Gimp or Photoshop or whatever  but I d really rather script it from the command line because there  are many of these things   An example of a non-working Image Magick command is   convert img1 png -background white -flatten img1-white png   That results in an error   Thanks

User · Answer

-background white -alpha remove -alpha off   Example   convert image png -background white -alpha remove -alpha off white png   Feel free to replace white with any other color you want  Imagemagick documentation says this about the -alpha remove operation      This operation is simple and fast  and does the job without needing   any extra memory use  or other side effects that may be associated   with alternative transparency removal techniques  It is thus the   preferred way of removing image transparency

User · Answer

here s how to replace the same image in all folders in a directory with white instead of transparent   mogrify -background white -flatten     png

User · Answer

Non-command line option  open the PNG file in Windows Paint and click Save

User · Answer

It appears that your command is correct so the problem might be due to missing support for PNG     You can check with convert -list configure or just try the following   sudo yum install libpng libpng-devel

User · Answer

This is not exactly the answer to your question  but I found your question while trying to figure out how to remove the alpha channel  so I decided to add this answer here   If you want to remove alpha channel using imagemagick  you can use this command   mogrify -alpha off     png

User · Answer

This works for me   convert -flatten img1 png img1-white png   Documentation references    -flatten command-line option -layers command-line option  -flatten is equivalent to -layers flatten

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I needed either  both -alpha background and -flatten  or -fill   I made a new PNG with a transparent background and a red dot in the middle    convert image png -background green -alpha off green png failed  it produced an image with black background  convert image png -background green -alpha background -flatten green png produced an image with the correct green background   Of course  with another file that I renamed image png  it failed to do anything  For that file  I found that the color of the transparent pixels was   d5d5d5  so I filled that color with green   convert image png  -fill green -opaque   d5d5d5  green png replaced the transparent pixels with the correct green

User · Answer

It s -alpha off  NOT -alpha remove  iOS app store upload fails when there is an alpha channel in any icon    Here s how to do it  mogrify -alpha off   png

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To actually remove the alpha channel from the file  use the alpha off option   convert in png -background white -alpha off out png

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I saw this question and answers which really help me but then I was needed to do it for a lot of files  So in case you have multiple images  PNG images  in one folder and you want to do it for all   find    -name    png  -exec convert    -flatten

User · Answer

The only one that worked for me was a mix of all the answers   convert in png -background white -alpha remove -flatten -alpha off out png

User · Answer

this creates an image just placing the 1st with transparency on top of the 2nd  composite -gravity center ImgWithTransp png BackgroundSameSizeOfImg png ResultImg png   originally found the tip on this post

User · Answer

Using -flatten made me completely mad because -flatten in combination with mogrify crop and resizing simply doesn t work  The official and for me only correct way is to  remove  the alpha channel   -alpha remove -alpha off  not needed with JPG   See documention  http   www imagemagick org Usage masking  remove

User · Answer

The Alpha Remove section of the ImageMagick Usage Guide suggests using the -alpha remove option  e g    convert in png  -background white  -alpha remove  out png      using the -background color of your choosing   The guide states      This operation is simple and fast  and does the job without needing any extra memory use  or other side effects that may be associated with alternative transparency removal techniques  It is thus the prefered way of removing image transparency    It additionally adds the note      Note that while transparency is  removed  the alpha channel will remain turned on  but will now be fully-opaque  If you no longer need the alpha channel you can then use Alpha Off to disable it     Thus  if you do not need the alpha channel you can make your output image size smaller by adding the -alpha off option  e g   convert in png  -background white  -alpha remove  -alpha off  out png     There are more details on other  often-used techniques for removing transparency described in the Removing Transparency from Images section   Included in that section is mention of an important caveat to the usage of -flatten as a technique for removing transparency      However this will not work with  mogrify  or with a sequence of multiple images  basically because the  -flatten  operator is really designed to merge multiple images into a single image    So  if you are converting several images at once  e g  generating thumbnails from a PDF file  -flatten will not do what you want  it will flatten all images for all pages into one image    On the other hand  using the -alpha remove technique will still produce multiple images  each one having transparency removed

User · Answer

Flattening image and applying background image is straight forward in ImageMagick  However  order of the commands is very important  To apply any background on a transparent image and flatten it  first apply the background than flatten it  The reverse doesn t work      convert sourceimage png -background BackgroundColor -flatten destinationimage png

User · Answer

Welp it looks like my decision to install  graphics magick  over  image magick  has some rough edges - when I reinstall genuine crufty old  image magick   then the above command works perfectly well   edit  a long time later  mdash  One of these days I ll check to see if  graphics magick  has fixed this issue

[png] Replace transparency in PNG images with white background

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