Post Reply 

png ?

Feb 1, 2012, 07:19
Post: #1
png ?
All right, I've got some questions about .png

Why are some of these checked and unchecked when saving

Quote:Interlacing (Adam7)
*Save background color
Save gamma
Save layer offset
*Save resolution
*Save creation time
*Save comment
*Save color values from transparent pixels
*Compression level: ---------9 "v"

*Default setting

Because I saved a png image just now and when I sent the image the color of the text was much brighter than the text on the Gimp program. I thought these settings might have something to do with it.

I've been wondering anyway. I usually check "save layer offset", as it helped once when an image would not save correctly.

Because

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Feb 1, 2012, 11:20
Post: #2
RE: png ?
Is there a color profile in the image?

Something to test:

1) note the RBG values the image background (in HTML "Hex": #rrggbb)
2) prepare a HTML file with a background set to the color above, and including the PNG
3) check for color discrepancies on the image border

The colors used in HTML aren't subject to color management, when the PNG will be if it has a color profile (unless this is disabled in the navigator options).

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Feb 13, 2012, 06:14
Post: #3
RE: png ?
Im not really sure what that means.

I know how to change the color from like grey scale -to- RGB. Do you means to prepare an HTML file, by opening up a color box to choose a color and manually choosing a matching color i.e. #000000? What means it color discrepancies, not sure.

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 21:15 (This post was last modified: Mar 6, 2012 21:17 by Pl3th0r4x.)
Post: #4
RE: png ?
Ok maybe I was not clear.

I have this image here a member wants me to create a transparent background for.

[Image: avatar_9-1.jpg]

Not sure if you can see here on but on their forum the image is coming out very pixalated around the borders

[Image: avatar_9-2.png]

I have included the xcf. In Gimp the image looks perfect with pixalation. Why is the finished product showing up blotchy?

I already added grow>alpha to color,


Attached File(s)
.xcf  avatar_9.xcf (Size: 21.98 KB / Downloads: 23)

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 21:34 (This post was last modified: Mar 6, 2012 21:39 by ofnuts.)
Post: #5
RE: png ?
Have you looked at your original image? It's crap. JPEG artifacts, big patch up to cover something (museum ID number?) and details in the wings border that are about pixel-size. Not sêaking of the white over whote that doesnt make for a very nice initial selection anyway.

You'll find the original picture here (caution: page really NSFW). Click on the picture to get a lager picture. Work from that.

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 22:26
Post: #6
RE: png ?
Awesome thanks, it came out perfectly and that page idk how you found it but it has some pretty cool and interesting photos.

[Image: th_Temple_of_dionysus.png?t=1331072667]

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 23:00
Post: #7
RE: png ?
(Mar 6, 2012 22:26)Pl3th0r4x Wrote:  Awesome thanks, it came out perfectly and that page idk how you found it but it has some pretty cool and interesting photos.

[Image: th_Temple_of_dionysus.png?t=1331072667]

Just googled for:
Code:
<--- google search at bottom of this scroll box to protect the innocent --->
<--- You have been warned. Some of you may want to bleach your
       eye pupils afterwards --->
<--- But then you have already see fun things in this thread --->







































"penis with wings"
.

This post wins the award for "most surrealistic" post of GimpForums for 2012.

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 23:19 (This post was last modified: Mar 6, 2012 23:22 by Pl3th0r4x.)
Post: #8
RE: png ?
It looks much better as his avatar, I asked him if he would prefer the wiener dog...he has not yet responded...



On further note. This seems to be a problem I have regularly with my little knowledge of Gimp. (come to think of it I do nothing else except read and study about computers and yet I am still clueless about so many things you would think I spend hardly any time on a PC at all).

Here is this image I have created.

[Image: dice.png]

It looks fine yes, but if you really get a good look on a darker background (or it may be clear here), the image has pixalation in the grooves! Grrr, is it a setting I need to change when saving, during creation, or an effect?

I only made two layers of text which I used a gradient on one, and a filter on the other "basic II" < I'm guessin g it was the latter. And a drop shadow.


Attached File(s)
.xcf  dice.xcf (Size: 143.96 KB / Downloads: 28)

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 6, 2012, 23:23
Post: #9
RE: png ?
Don't see anything bad... it's not more pixellated than what my display resolution makes it. Any specific spot to check?

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 01:18 (This post was last modified: Mar 7, 2012 01:19 by Pl3th0r4x.)
Post: #10
RE: png ?
Just the grooves. The grooves arent smooth they have like jaged edges. (the grooves within the text.)

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 09:32
Post: #11
RE: png ?
I was not looking inside since you mentioned it was more visible on a suitable background.

So, brace yourself, you have just been hit by a mathematical theorem... What happened to your image is that the final scaling down generated aliasing due to spatial frequency folding (the link above has a good example for pictures).

So the solution is to apply a low-pass filter, which, in image processing, is just a gaussian blur. The rule of thumb is that if you scale down your image by X, you apply a gaussian blur of X pixels. Of course this blurs the bigger image, but it doesn't remove any detail you would keep properly in the scaled down image.

In your case, you scaled down by 64% (1.6x reduction) so you should apply a 1.6-2px blur. You can recover some sharpness after the downscale by a sharpening filter such as "Filters/Enhance/Unsharp mask". In the image below from top to bottom:
  • Scaled down without pre-blur
  • Scaled down with 2px pre-blur
  • Scaled down with 2px pre-blur and unsharp mask applied with default settings (5.0/0.5/0.0)
  • Scaled down with 2px pre-blur with unsharp mask applied with my pet settings for photography (1.0/1.0/0.0)

[attachment=990]

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 22:56
Post: #12
RE: png ?
K I see what you are saying except as for the mathematical theorem; I've done my fair share of taking notes from wiki, and this could be the first one I finished carefully reading through and felt like I knew less after reading it.

As for your new user title. Now that was an interesting read. Had no idea there was a syndom for that.

Lastly I did make the image as you said and I totally understand. I was trying to do it for this image though and it is not the same.

[Image: dicealien.jpg?t=1331158275]

[Image: dicealien-1.png?t=1331158346]

I just made the back bround transparent, color to alpha.

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 23:11 (This post was last modified: Mar 7, 2012 23:15 by ofnuts.)
Post: #13
RE: png ?
Your background isn't black... Use the color picker, you'll find #141517. And it's not uniform either, there are JPEG artifacts. Extracted using #141517 as the background color:

[attachment=996]

On a white BG, you'll notice the "shadow" (which demonstrates the background isn't uniform), the JPEG compression artifacts, and the rim caused by a butchered re-sharpening.

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 23:37 (This post was last modified: Mar 7, 2012 23:37 by Pl3th0r4x.)
Post: #14
RE: png ?
But this does not ansewr the question at hand. Are you saying to alter the color settings? Instead of color to alpha to ´white' you are saying to color to alpha the offset black' color?

[Image: banana.gif]
Find all posts by this user
Quote this message in a reply
Mar 7, 2012, 23:53
Post: #15
RE: png ?
(Mar 7, 2012 23:37)Pl3th0r4x Wrote:  But this does not ansewr the question at hand. Are you saying to alter the color settings? Instead of color to alpha to ´white' you are saying to color to alpha the offset black' color?
Of course. In C2A, the color to use is the real color of your background. The definition of C2A is to change you image into something with transparent bits, so that if you place this new image over a background of the color subtracted by C2A, you get back the original image...

Now answering your questions on
https://Gimp-Forum.net
Visit this user's website Find all posts by this user
Quote this message in a reply
Post Reply 


Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Editing an Un-editable png with GIMP jasonmzs 1 325 Jun 16, 2014 09:09
Last Post: ofnuts
  .xcf to .png Unisus41 8 1,931 May 3, 2014 16:22
Last Post: cki
  How to export as png kudorgyozo 7 679 Mar 19, 2014 16:40
Last Post: rich2005
  .png thumbnail image Barbie 6 636 Mar 13, 2014 08:16
Last Post: iForStyle007
  export to png - no settings avaliable barmalei 7 889 Dec 1, 2013 21:37
Last Post: barmalei

Forum Jump:


GIMP ForumPortalArchiveContactTermsRSS