06-14-2021, 08:10 AM
My take on it.
Of course it does. Gimp is a raster (bitmap) editor where the images is composed of rectangular pixels. A 20 x 20 image = 400 pixels, Scaling x2 and while most people think in linear units that gives a 40 x 40 image = 1600 pixels a four times increase in size.
Then there is compression. Although png is lossless it is compressed, the default is maximum compression. A 400 x 400 one layer with a single colour, file size 1 KB , filled with a multicolour gradient, file size 48 KB
Then bit depth, I managed to find a 72 MB 8 bit RGB PNG, a nice colourful old map about 6400 x 5600 pix That is reported bottom of the Gimp window as 336 MB That is memory used by Gimp not file size , the value will swell with add layers, undo information held by Gimp.
Without any scaling the exported file size will increase (1) Add an Alpha Channel 72 MB -> 81 MB (2) Increase the bit depth File -> Precisionabove 8 bit , export and get a 16 bit image file = 112 MB
In Edit -> Preferences -> Image Import & Export -> Import Policies there is an option to both increase bit depth and add an alpha chanel automatically. Check that.
I can go the other way, export as grayscale = 24 MB or convert to color indexed (256 colours) 2.5 MB. Beware of programs that give small png files, they might be indexed.
Gimp .xcf saved files are roughly parallel, although larger, internal compression is not as great. Any extra layers, masks, channels all contribute to the file.
AFAIK snipping tool = screen capture, bound to be smaller, the image size width x height is limited by monitor size, what you get is a scaled down image.
Quote:...snip..Does scaling increase the file size quite a bit? ..
Of course it does. Gimp is a raster (bitmap) editor where the images is composed of rectangular pixels. A 20 x 20 image = 400 pixels, Scaling x2 and while most people think in linear units that gives a 40 x 40 image = 1600 pixels a four times increase in size.
Then there is compression. Although png is lossless it is compressed, the default is maximum compression. A 400 x 400 one layer with a single colour, file size 1 KB , filled with a multicolour gradient, file size 48 KB
Then bit depth, I managed to find a 72 MB 8 bit RGB PNG, a nice colourful old map about 6400 x 5600 pix That is reported bottom of the Gimp window as 336 MB That is memory used by Gimp not file size , the value will swell with add layers, undo information held by Gimp.
Without any scaling the exported file size will increase (1) Add an Alpha Channel 72 MB -> 81 MB (2) Increase the bit depth File -> Precisionabove 8 bit , export and get a 16 bit image file = 112 MB
In Edit -> Preferences -> Image Import & Export -> Import Policies there is an option to both increase bit depth and add an alpha chanel automatically. Check that.
I can go the other way, export as grayscale = 24 MB or convert to color indexed (256 colours) 2.5 MB. Beware of programs that give small png files, they might be indexed.
Gimp .xcf saved files are roughly parallel, although larger, internal compression is not as great. Any extra layers, masks, channels all contribute to the file.
Quote: As a temporary fix I used the Snipping Tool to create a new PNG file from the 397 meg and it's a small 682 KB PNG file - 500x smaller
AFAIK snipping tool = screen capture, bound to be smaller, the image size width x height is limited by monitor size, what you get is a scaled down image.