In Object Styles you can specify in the Object Export Section
Export Options > EPUB and HTML > User defined raster > Format
You need only to apply the correct object style to an image.
This option is available in InDesign 9.0 and higher.
Good suggestion. But it appears one has to do this for every image. Is there not a global setting to force inline images to export to epub as jpeg? I agree with David, the options aren't great.
Unless I'm misunderstanding, set your default image format in File > Export > EPUB > Image > Image Conversion > [file format]
For images which you want to handle differently, create an Object Style as Willi described, and apply it to images which are the exception.
Perhaps my explanation was unclear.
Key words here are *inline anchored*.
ID treates inline anchored images *differently* from all other images (non-anchored, or anchored with position=custom).
For anchored images, ID exports ALL images as PNG.
For all other images, ID exports JPEGs as JPEG and PNGs as PNG.
This is not desirable, nor is it rational. I think it might be a bug.
I don't want to set a global setting to have *all* my images exported as JPEG. I may have some placed PNGs that I want to keep as PNG.
I just want ID to *not* convert all my images to PNG (regardless of their original type), just because they happen to have been placed as inline anchored images.
Does that help clarify the issue?
Yes. I am experiencing the same thing. I would think if you export ePUB and set the Image Conversion to "Automatic" then JPEGs should export to JPEGs and PNGs export to PNGs. Right now, all my inline and anchored JPEGs are converting to PNGs. What gives?
When I set File > Export > EPUB > Image > Image Conversion > to "Automatic" it still exports all my nice inline and anchored JPEGs to PNGs. Is that expected? I would have thought the original format would be intact.
Here's the definition from the InDesign Help file:
Lets you choose whether the optimized images in your document are converted to GIF, JPEG, or PNG. Choose Automatic to let InDesign decide which format to use in each instance. Choosing PNG disables the image compression settings; use PNG for lossless images or for images that include transparency.
Choosing Automatic means InDesign decides which format to use. It doesn't mean keep the same format.
Okay. But why does InDesign decide to use PNG for ALL inline or anchored images? They are frequently not the best choice (especially for size). What makes InDesign decide to convert those JPEGs to PNG?
But you can choose your own settings. You don't have to rely on "Automatic."
That is what I end up doing. Choosing JPEG instead of Automatic. Then making any PNG or GIF one-offs in Object > Object Export Options, depending upon what the artwork happens to be. Thanks for the feedback. It's been helpful. Cheers!
...because it is a bug. It will be fixed in the next InDesign CC update.
Architect, InDesign Engineering
There are no bugs in InDesign.
Just features that need to be refined.
I do like the "changes" language as it removes a lot of tension.
That's why this document (helpx.adobe.com/pdf/InDesign_EPUB_Changes_from-CS6-to-CC.pdf) intentionally says "changes"...not fixes.
Architect, InDesign Engineering
... That's funny!
Serious question related to this, tho:
EPUBs I have worked on often need to be cracked open, and then the files processed through Photoshop in order to get them to weigh much less. Some EPUB vendors like Kindle have a size cap requirement. Is there a trick I don't know about, or how do we get the image export to make tinier image files at correct weight the at the time of exporting to EPUB? IOW, can I avoid the extra work? I wish for a future where I don't *generally* have to crack open the zipped up EPUB.
I hope that is a clear question.
Mike Witherell in Maryland
I think the threshold is 50 MB. I also had to reduce the size of the photos in PS to comply with Kindle. When exporting to Kindle I choose Copy images/Original because with the other option Copy/images Optimized the images look too small.