Upon using ExifRead (https://pypi.org/project/ExifRead/) to processes exif metadata from an image and using that to extract the Jpeg Thumbnail, we came to know that the extract_thumb method, instead of extracting the Jpeg Thumbnail, will extract the Jpeg Preview of a RAW image. Is this a desired behavior and if so, is there a way to extract the actual Jpeg Thumbnail from the image?
Also, in case the Jpeg Preview is missing, will Libraw report and error or extract the Jpeg Thumbnail instead?
More information about this issue can be found at the discussion here: https://github.com/letmaik/rawpy/issues/96
Thanks!
unpack_thumb() provides
unpack_thumb() provides largest available thumbnail/preview/whatever-it-called.
-- Alex Tutubalin @LibRaw LLC
pixel position of thumbnail image vs. of raw image
Dear Alex,
first of all, many thanks for the wonderful libraw and your effort.
I'm currently dealing with Canon R5 CR3.
I can sucessfully decode the largest thumbnail(JPEG 1620x1080) using this following code.
//--------------------
rawp->unpack_thumb_ex(1);
rawimgthumb = rawp->dcraw_make_mem_thumb(&err); //store unpacked and processed raw image
Mat rawData(1, rawimgthumb->data_size, CV_8UC1, (void*)rawp->imgdata.thumbnail.thumb);
thumbimg_file = imdecode(rawData, 1); //BGR
//--------------------
Howerver, it seems that the start pxiel(left-top conner) of the decoded thumbnail image is not the same of the start pixel of the raw image(8191x5463 or with frame 8352x5586).
How can we match the exackt position between the thumbnail and the raw image?
Is there any parameter about the croping region of the thumbnail from raw image?
Thank you for your response in advance.
Kim
Kim
We don't know of a general
We don't know of a general answer to this question that will always work.
For example:
In some cases imgdata.sizes.raw_inset_crops[..] may work.
-- Alex Tutubalin @LibRaw LLC
many thnaks for the prompt
many thnaks for the prompt response.
i'll try to test the parameter imgdata.sizes.raw_inset_crops[..].
best regards.
Kim