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[Q] Resizing a PNG makes it BIGGER!

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[Q] Resizing a PNG makes it BIGGER! Daniel Carrera 05 Jun 01:59
  [Q] Resizing a PNG makes it BIGGER! Marco Wessel 05 Jun 02:12
   [Q] Resizing a PNG makes it BIGGER! Daniel Carrera 05 Jun 02:26
    [Q] Resizing a PNG makes it BIGGER! Jonathan E. Paton 05 Jun 11:30
     [Q] Resizing a PNG makes it BIGGER! Daniel Carrera 05 Jun 20:11
  [Q] Resizing a PNG makes it BIGGER! Sven Neumann 05 Jun 13:31
   [Q] Resizing a PNG makes it BIGGER! Daniel Carrera 05 Jun 20:12
    [Q] Resizing a PNG makes it BIGGER! Sven Neumann 05 Jun 20:56
Daniel Carrera
2003-06-05 01:59:19 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

Hi,

This is really weird. I have a PNG image. I tried to make it smaller by resizing it down, but instead it got BIGGER. I don't understand this at all.

I put the images on the web:

Original: http://www.math.umd.edu/~dcarrera/screenshot.png Resized: http://www.math.umd.edu/~dcarrera/screenshot_resized.png

With width and height of the resized image are 0.8 times the size of the original, so I would have imagined that the resized image would be 0.8*0.8 = 0.64 times the size of the original, but that's not the case:

$ du -sk * 52 screenshot.png
128 screenshot_resized.png

The new image is over 4 times bigger than the original!

These are RGB images BTW, but that shouldn't cause this.

Does anyone know what's happening?

Thanks.

Marco Wessel
2003-06-05 02:12:22 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

My guess is that this is because of the interpolation when resampling. Makes it less easily compressable. (Notice the 'anti-aliased' edges in the resized picture?)

Marco Wessel

On Wed, 4 Jun 2003, Daniel Carrera wrote:

Hi,

This is really weird. I have a PNG image. I tried to make it smaller by resizing it down, but instead it got BIGGER. I don't understand this at all.

I put the images on the web:

Original: http://www.math.umd.edu/~dcarrera/screenshot.png Resized: http://www.math.umd.edu/~dcarrera/screenshot_resized.png

With width and height of the resized image are 0.8 times the size of the original, so I would have imagined that the resized image would be 0.8*0.8 = 0.64 times the size of the original, but that's not the case:

$ du -sk * 52 screenshot.png
128 screenshot_resized.png

The new image is over 4 times bigger than the original!

These are RGB images BTW, but that shouldn't cause this.

Does anyone know what's happening?

Daniel Carrera
2003-06-05 02:26:26 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

On Thu, Jun 05, 2003 at 02:12:22AM +0200, Marco Wessel wrote:

My guess is that this is because of the interpolation when resampling. Makes it less easily compressable. (Notice the 'anti-aliased' edges in the resized picture?)

Marco Wessel

Any suggestion as to how to fix it?

Jonathan E. Paton
2003-06-05 11:30:29 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

--- Daniel Carrera wrote:

On Thu, Jun 05, 2003 at 02:12:22AM +0200, Marco Wessel wrote:

My guess is that this is because of the interpolation when resampling. Makes it less easily compressable. (Notice the 'anti-aliased' edges in the resized picture?)

Marco Wessel

Any suggestion as to how to fix it?

Retake the screenshot, after reducing the size of the window. Really. Resizing without anti-aliasing is like cutting 1 pixel slivers out of the image, and can make vertical or horizontal lines disappear out of the image.

At 52Kb, the image size is satisfactory for broadband/LAN users. If the image is to be used on the web, why not consider using the image size attributes of HTML to automatically rescale the image?

http://www.w3.org/TR/html4/struct/objects.html#h-13.2 http://www.w3.org/TR/html4/struct/objects.html#visual

You could also reduce the colour depth without any noticable drop in quality. Applications usually keep to a 256 colour default pallet.

Magic bullets not found here.

Jonathan Paton

===== #!perl
$J=' 'x25 ;for (qq< 1+10 9+14 5-10 50-9 7+13 2-18 6+13 17+6 02+1 2-10 00+4 00+8 3-13 3+12 01-5 2-10 01+1 03+4 00+4 00+8 1-21 01+1 00+5 01-7 >=~/ \S\S \S\S /gx) {m/( \d+) (.+) /x,, vec$ J,$p +=$2 ,8,= $c+= +$1} warn $J,,

___

Sven Neumann
2003-06-05 13:31:47 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

Hi,

Daniel Carrera writes:

This is really weird. I have a PNG image. I tried to make it smaller by resizing it down, but instead it got BIGGER. I don't understand this at all.

I put the images on the web:

Original: http://www.math.umd.edu/~dcarrera/screenshot.png Resized: http://www.math.umd.edu/~dcarrera/screenshot_resized.png

With width and height of the resized image are 0.8 times the size of the original, so I would have imagined that the resized image would be 0.8*0.8 = 0.64 times the size of the original, but that's not the case:

$ du -sk * 52 screenshot.png
128 screenshot_resized.png

The new image is over 4 times bigger than the original!

128 / 52 = 2.46

These are RGB images BTW, but that shouldn't cause this.

Actually these are RGBA images. If you want to reduce the file size, you'd better flatten the image since I don't see any alpha information.

Sven

Daniel Carrera
2003-06-05 20:11:07 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

On Thu, Jun 05, 2003 at 10:30:29AM +0100, Jonathan E. Paton wrote:

Retake the screenshot, after reducing the size of the window.

If you look at what the screenshot is of, you will notice that I can't make the window much smaller since that would hide information, or pack it very tightly.

At 52Kb, the image size is satisfactory for broadband/LAN users. If the image is to be used on the web, why not consider using the image size attributes of HTML to automatically rescale the image?

No, that's not what the image is for. I am writing a small manual on the use of OpenOffice Writer. It has many screenshots and together they do add up.

You could also reduce the colour depth without any noticable drop in quality. Applications usually keep to a 256 colour default pallet.

Yeah, I was thinking to do that. Thanks.

Daniel Carrera
2003-06-05 20:12:58 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

On Thu, Jun 05, 2003 at 01:31:47PM +0200, Sven Neumann wrote:

$ du -sk *
52 screenshot.png
128 screenshot_resized.png

The new image is over 4 times bigger than the original!

128 / 52 = 2.46

Okay, I forgot how to divide. But still.

These are RGB images BTW, but that shouldn't cause this.

Actually these are RGBA images. If you want to reduce the file size, you'd better flatten the image since I don't see any alpha information.

Thanks. I didn't realize that they were. How do you tell appart an RGBA image from an RGB image? Gimp calls them both "RGB".

Sven Neumann
2003-06-05 20:56:19 UTC (almost 21 years ago)

[Q] Resizing a PNG makes it BIGGER!

Hi,

Daniel Carrera writes:

Thanks. I didn't realize that they were. How do you tell appart an RGBA image from an RGB image? Gimp calls them both "RGB".

I used "file foo.png" but there are lots of indicators in GIMP as well. The most obvious is probably if you can Flatten the image or not.

Sven