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

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

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


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

On 4/07/24 5:31 am, HenHanna wrote:

thank you...ÿ so it seems the GIF file is smaller but
ÿÿÿÿÿÿÿÿÿÿÿÿÿ can show fewerÿ 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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Subject: 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> 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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