Subject: Re: Windows freeware to lock in a 3: or 4:3 aspect ratio for cropping
In article <email@example.com>, Mayayana<firstname.lastname@example.org> wrote:
> That's what all raster images are. Pixel grids. Bitmaps.
> No raster image format stores anything different. They
> just store it in different ways, with varying degrees
> of damage to the image.
there is no damage.
> JPG degrades the image to make
> it compress better, with less color variety.
it's entirely up to the user what the jpeg quality/compression level
is, and at its highest quality, a jpeg is indistinguishable from the
original. this is very easy to demonstrate, should you not believe it.
> GIF reduces
> to 256 colors and compresses that. (256 colors requires
> an embedded color table, which takes up extra space,
> but then each pixel can be stored as a single byte.)
a colour table takes up very little space.
> I don't know how PNG works
> but I'm guessing it's
> basically a BMP in a ZIP, with the addition of alpha
> channel data (transparency) requiring 4 bytes per pixel.
> (GIF, by contrast, stores transparency data by indentifying
> one specific color that's not to be painted onscreen.)
true, and primitive.
> TIF, likewise, is basically a BMP in a ZIP.
> (Though a ZIP
> can often shrink a BMP by 90%,
simple logos with large areas of solid colours might shrink that much,
but certainly not with photos. logos would be better served with a gif
or png, not a zipped bmp.
> while a TIF seems to only
> manage about 50%. I don't know why.)
yep. you sure don't.
> They're all just ways to store a BMP. None of those
> image formats means anything until the BMP is extracted.
> One can't render a JPG onscreen any more than the words
> of a ZIPped Word DOC can be read from the ZIP bytes.
> It has to be decompressed to get the BMP.
decompressed, yes, but no bmp.
> Similarly, when one applies filters in an editing program
> it's just a math formula applied to the bitmap bytes.
> Sharpening increases the difference between the numeric
> values. Interpolation for resizing calculates a new pixel
> grid by examining the values of neighboring pixels.
> Lightening increases the byte values of the pixel bytes.
that part is mostly true. it's more complex than that, but i'll spare
you the details.
> It's all just math operations on 3-byte RGB pixels stored
> as grids in a BMP.
what you *refuse* to understand is that it doesn't have to be (and
normally is *not*) a bmp.
also, 3 bytes is horribly outdated. these days, it's two bytes per
component or it's a floating point value, with each pixel often having
more than 3 components (rgba, cmyk, hexachrome, etc.)
> In other words, the idea that BMP is outdated is a
> misunderstanding of what raster images are.
any misunderstanding is entirely with you.
bmp is obsolete. period.