Search found 1147 matches

by glennrp
2017-03-28T08:55:41-07:00
Forum: Bugs
Topic: PNG expected N bytes; found N bytes.
Replies: 1
Views: 4641

Re: PNG expected N bytes; found N bytes.

"Identify" only reads the header, and in this case there is nothing wrong with the header. If you ask "identify" to provide more details (with "identify -verbose" or "identify -format...") then it reads the entire file and discovers that it's truncated. You can force "identify" to check the entire f...
by glennrp
2017-03-26T12:36:47-07:00
Forum: Developers
Topic: Option to not reduce/freeze Indexed Palette
Replies: 15
Views: 16073

Re: Option to not reduce/freeze Indexed Palette

Sorry I don't have the magick spell, although I'm looking for it. With the sample image
provided, "-define png:preserve-colormap" causes the image to be written as RGBA
rather than indexed, which is obviously a bug.
by glennrp
2017-03-26T11:30:10-07:00
Forum: Developers
Topic: Option to not reduce/freeze Indexed Palette
Replies: 15
Views: 16073

Re: Option to not reduce/freeze Indexed Palette

I'm not sure what you are expecting. The "PNG8:" prefix means, "please generate a reduced palette" while
png:preserve-colormap means "please do not generate a new palette".

But I have verified that the PNG palette does indeed get lost when -define png:preserve-colormap is used.
by glennrp
2017-03-08T17:37:33-07:00
Forum: Users
Topic: What does the -define jpeg:size option concretely do?
Replies: 6
Views: 4609

Re: What does the -define jpeg:size option concretely do?

I believe that in such cases the JPEG reader will recognize that the hint is too small and use a value that is the next power-of-2 size larger than the target size.
by glennrp
2017-03-08T17:21:31-07:00
Forum: Users
Topic: How to handle tifs over 2 GB?
Replies: 12
Views: 7344

Re: How to handle tifs over 2 GB?

PNG is also limited to 2Gx2G
by glennrp
2017-02-28T09:16:20-07:00
Forum: Bugs
Topic: Wrong imange conversion with PNG files
Replies: 3
Views: 3323

Re: Wrong imange conversion with PNG files

Perhaps you have not installed libpng or have not linked ImageMagick with libpng. Type "convert -version" or "magick -version" and see if "png" is listed among the delegates.
by glennrp
2017-02-28T08:54:18-07:00
Forum: Users
Topic: What does the -define jpeg:size option concretely do?
Replies: 6
Views: 4609

Re: What does the -define jpeg:size option concretely do?

For JPEG, the size option (or jpeg:size option) provides a hint to the JPEG decoder
that it can reduce the size on-the-fly during decoding. This saves memory because
it never has to allocate memory for the full-sized image (assuming the "size" is smaller
than the original dimensions!).
by glennrp
2017-01-28T13:50:58-07:00
Forum: Users
Topic: trim +repage animated gif issue
Replies: 19
Views: 10323

Re: trim +repage animated gif issue

Your injput.gif contains offsets. "magick identify -verbose input.gif" says, for the first frame, "Page geometry: 374x416+70+4"
by glennrp
2017-01-27T12:38:57-07:00
Forum: Bugs
Topic: There are gray stains on the image after converting to another format after use ImageMagick php
Replies: 2
Views: 2844

Re: There are gray stains on the image after converting to another format after use ImageMagick php

I saw this same question on Stackexchange about 4 days ago and gave the same answer as snibgo's, but apparently it didn't help the person, who said changing quality to 100 did no help. I'm wondering if this is the old-ghostscript-version problem. Valentinn, please try converting to PNG or to PPM ins...
by glennrp
2017-01-22T13:27:09-07:00
Forum: Developers
Topic: New PNG chunks: caNv and exIf
Replies: 0
Views: 12196

New PNG chunks: caNv and exIf

I've checked a new chunk handler into IM6 and IM7 that recognizes the "caNv" (canvas) chunk. This is intended to replace the existing vpAg (virtual page) chunk. The differences are (1) the caNv chunk contains its own offset values while vpAg relied upon the oFFs chunk to carry the offsets separately...
by glennrp
2017-01-21T08:50:28-07:00
Forum: Users
Topic: Best compression level for PNG
Replies: 5
Views: 9564

Re: Best compression level for PNG

Compression level 9 (like GIMP) is "-quality 90" (for no PNG filtering) or "-quality 95" (for adaptive PNG filtering).
by glennrp
2017-01-20T16:12:16-07:00
Forum: Users
Topic: -define png:size={size}?
Replies: 11
Views: 8636

Re: -define png:size={size}?

I've posted a feature request to the libpng mailing list, here: https://sourceforge.net/p/png-mng/mailman/png-mng-misc/thread/1159291813.1125196.1484857317904%40mail.yahoo.com/#msg35614399 I didn't see it. Now that you mentioned it here, I hunted for it and found your message in my spam folder. Tha...
by glennrp
2017-01-20T15:53:52-07:00
Forum: Users
Topic: -define png:size={size}?
Replies: 11
Views: 8636

Re: -define png:size={size}?

What is the nature of your 50mb PNG files? Are they drawings, aero photos, maps, or what? Are they RGB, RGBA, indexed? All of these would be useful for figuring out how to proceed here.
by glennrp
2017-01-20T15:50:26-07:00
Forum: Users
Topic: -define png:size={size}?
Replies: 11
Views: 8636

Re: -define png:size={size}?

I'm looking at the libpng manual , and I'm wondering if that change will only work for interlaced images. correct. With non-interlaced images, would ImageMagick be able to read in only a sample of the rows? I assume that this part about reading in one row at a time suggests it's possible: If you do...
by glennrp
2017-01-20T15:41:29-07:00
Forum: Users
Topic: -define png:size={size}?
Replies: 11
Views: 8636

Re: -define png:size={size}?

The most reduction you can get by skipping interlace passes is 64:1 (only display one dot for each 8x8 block of pixels). But as I said you probably won't like the result. It would be OK for photos, but any fine detail is going to be lost. I'll work up a demo -- but in the meantime, look at Greg Roel...