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in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?)

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  in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) HenHanna <HenHanna@devnull.tb> - 2024-07-02 08:02 -0700
    Re: in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) Pieter van Oostrum <pieter-l@vanoostrum.org> - 2024-07-03 13:22 +0200
      Re: in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) Greg Ewing <greg.ewing@canterbury.ac.nz> - 2024-07-04 03:36 +1200
        Re: in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) HenHanna <HenHanna@devnull.tb> - 2024-07-03 10:31 -0700
          Re: in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) Greg Ewing <greg.ewing@canterbury.ac.nz> - 2024-07-04 10:24 +1200
        Re: in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?) Pieter van Oostrum <pieter-l@vanoostrum.org> - 2024-07-05 13:54 +0200

#196355 — in a program like this, it makes NO difference , whether i save as PNG or GIF ? (size?)

in a program like this, it makes NO difference
                               whether i save as PNG  or  GIF ?

                                  (is one smaller than the other?)

black= (0,0,0)
white= (255,255,255)  .............

from PIL import Image
from PIL import ImageDraw

def newImg():
     img = Image.new('RGB', (120, 120))

     for i in range(100):
        img.putpixel((10+i,10+i),   (red, black, white)[i%3])

     img.save('test.gif')
     return img

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#196363

HenHanna <HenHanna@devnull.tb> writes:

> in a program like this, it makes NO difference
>                               whether i save as PNG  or  GIF ?
>
>                                  (is one smaller than the other?)
>
> black= (0,0,0)
> white= (255,255,255)  .............
>
> from PIL import Image
> from PIL import ImageDraw
>
> def newImg():
>     img = Image.new('RGB', (120, 120))
>
>     for i in range(100):
>        img.putpixel((10+i,10+i),   (red, black, white)[i%3])
>
>     img.save('test.gif')
>     return img
>

In general a 'PNG' image has better quality than 'GIF'. In a 'PNG' image all the pixels that the program generated are still present, exactly as they were generated. In a 'GIF' image, however, pixels may have been altered in order to accommodate a smaller file size. For photo-like images the difference is usually not directly visible to the eye, except when you zoom in considerably. For line-art drawings and images with sharp edges, the effect may well be visible to the naked eye.

In your particular image, there appears to be no difference: all the pixels are present as generated. But this is an exception for 'GIF' images.
-- 
Pieter van Oostrum <pieter@vanoostrum.org>
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]

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#196364

On 3/07/24 11:22 pm, Pieter van Oostrum wrote:
> In general a 'PNG' image has better quality than 'GIF'. In a 'PNG' image all the pixels that the program generated are still present, exactly as they were generated. In a 'GIF' image, however, pixels may have been altered in order to accommodate a smaller file size.

I think you're thinking of JPEG. PNG and GIF both use lossless 
compression, however GIF only supports 8-bit colour and 1-bit 
transparency. For images with no more than 256 distinct colours, PNG and 
GIF will probably give identical results.

-- 
Greg

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#196365

On 7/3/2024 8:36 AM, Greg Ewing wrote:
> On 3/07/24 11:22 pm, Pieter van Oostrum wrote:
>> In general a 'PNG' image has better quality than 'GIF'. In a 'PNG' 
>> image all the pixels that the program generated are still present, 
>> exactly as they were generated. In a 'GIF' image, however, pixels may 
>> have been altered in order to accommodate a smaller file size.


> 
> I think you're thinking of JPEG. PNG and GIF both use lossless 
> compression, however GIF only supports 8-bit colour and 1-bit 
> transparency. For images with no more than 256 distinct colours, PNG and 
> GIF will probably give identical results.
> 

thank you...  so it seems the GIF file is smaller but
               can show fewer  colors.

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#196366

On 4/07/24 5:31 am, HenHanna wrote:
> thank you...  so it seems the GIF file is smaller but
>                can show fewer  colors.

I think it depends on the image. Wikiopedia suggests that GIF
can be smaller for small images, whereas PNG tends to be smaller
for larger 8-bit images.

-- 
Greg

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#196374

Greg Ewing <greg.ewing@canterbury.ac.nz> writes:

> On 3/07/24 11:22 pm, Pieter van Oostrum wrote:
>> In general a 'PNG' image has better quality than 'GIF'. In a 'PNG'
>> image all the pixels that the program generated are still present,
>> exactly as they were generated. In a 'GIF' image, however, pixels may
>> have been altered in order to accommodate a smaller file size.
>
> I think you're thinking of JPEG. PNG and GIF both use lossless
> compression, however GIF only supports 8-bit colour and 1-bit
> transparency. For images with no more than 256 distinct colours, PNG and
> GIF will probably give identical results.

Sorry, you are right. I never use GIF anymore, so indeed I read JPG instead.
-- 
Pieter van Oostrum <pieter@vanoostrum.org>
www: http://pieter.vanoostrum.org/
PGP key: [8DAE142BE17999C4]

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