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Resizing pictures (DPI)

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  • Susanne Nyrop
    Dafne: When you talk about the size of a file it is not (only) the number of pixels - it also depends on the quality of resolution, that is the sharpness of
    Message 1 of 4 , Mar 2, 2002
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      Dafne:

      When you talk about the size of a file it is not (only) the number of
      pixels - it also depends on the quality of resolution, that is the
      sharpness of colors and contrasts - the larger file, the better
      resolution (necessary for a perfect color print), and the smaller
      file, the faster it will load on the internet! That is why the scale
      of "Dots per Inch" (DPI) has a great importante to us web designers
      (in spe:-) Less dots, faster load.
      "Millions of colors " are much more information-rich than , say, 256
      colors which is usually enough for getting a neat image on a computer
      screen - but will look pale in print.

      I think the most reliable image formats for the net are GIF and
      PICT. Many (or all?) scanner/ image programmes do not make those
      formats; I have found that when I open my scanner Twain resource in
      the shareware programme Graphic converter, I can decide for almost
      any format. You will be able to check the file size somewhere in your
      informations - a reasonable size for a smaller image might be less
      than 100 kb. For the size in inches or centimeters, The homepage
      images will not always correspond with your WYSIWYG pagemaker - that
      may depend on the browser type and version, and the screen resolution
      - which is (I think) also meassures in dots per inch - DPI. I usually
      have a low resolution, 800 x 600, that will give me clear fonts and
      a good contrast (And is the recommended resolution for Tapped In).

      Just an example: I opened my test pages on the net from another
      computer yestedrday, and got a realive surprise: my background colors
      and my images were totally different (far too edark for my liking).
      This made me realize how important ist may be to test homepages on
      different screen resolutions, and different browsers (even different
      browser versions). That is one more reason why I have not yet felt
      ready to share my HTML homework - it does not work orderly yet, many
      of the links are still unchecked and I have no content on some of my
      pages. I know a lot of the problems, and need a little more time to
      correct the most obvious problems. One of these days ...:-)

      Sus





      >Hi Everybody,
      >
      >Taking on this week's topic I would like to express my ignorance
      >about resizing pictures. I have three applications that do the work:
      >Paint, Microsoft Photo Editor and PhotoStudio 2000 (this one came
      >with my webcam). I have managed to resize my pictures for the
      >webpage. But I do not know how I have done it. I mean, I start trying
      >until I get a size that fits the available space and is easy to
      >download, but I do not know how to get a specific size, neither know
      >I which are the recommendable sizes. For instance, if I use Microsoft
      >Photo Editor, I go to "Image", and then to "Change Size". There, I
      >find the units in pixels, inches and cm, well, I never know how to
      >set this. Sometimes I change the pixels and the picture is still too
      >large. Until I try the picture on the webpage I do not know if it will
      >fit there or not. If I use PhotoStudio, it has a reducing feature
      >expressed in figures like 1:1,1:3, etc. I am lost. I heard someone
      >say that a good size for web pictures was 72 pixels by inch. Is this
      >right? If so, How do I get that?
      >I am all ears for advice.
      >
      >Lost in cyber pictures,
      >Dafne
      >
      >
      >
      >
      >
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    • Vance Stevens
      Thanks Dafne for starting the ball rolling on the questions. I ve seen Susanne s response and she is correct that dots per inch or density of information has
      Message 2 of 4 , Mar 2, 2002
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        Thanks Dafne for starting the ball rolling on the questions.

        I've seen Susanne's response and she is correct that dots per inch or density
        of information has much to do with the FILEsize of an image and therefore how
        long it will take to download over the Internet.

        It's much easier to control the filesize of an image though two other means:
        cropping and resizing.

        My favorite tool for doing these operations is Thumbs Plus,
        http://www.cerious.com . Using this tool, you browse your hdd for images and
        click on the thumbs icons to see their thumbnails. You can then click on an
        image to bring it up and drag a box on it to crop it (Edit/Crop), or use Image
        / Rotate & Resize to make the picture smaller.

        One nice feature of this program is the Options / Preferences features. The
        File List tab for example allows you to display the File Size in bytes and
        Dimensions in pixels of your image. It's very handy to have this information
        right in front of you when viewing images. As Susanne mentioned, you want to
        keep your file sizes down to well below 100 kbytes, in fact below 50 in most
        cases, for fast download to your vistors' browsers.

        dygonza wrote:

        > Hi Everybody,
        >
        > Taking on this week's topic I would like to express my ignorance
        > about resizing pictures. I have three applications that do the work:
        > Paint, Microsoft Photo Editor and PhotoStudio 2000 (this one came
        > with my webcam).

        I've launched Microsoft PhotoDraw 2000 and I can see that I can drag the image
        smaller though I can't specify a filesize as I can with Thumbs Plus.

        > I have managed to resize my pictures for the
        > webpage. But I do not know how I have done it. I mean, I start trying
        > until I get a size that fits the available space and is easy to
        > download, but I do not know how to get a specific size, neither know
        > I which are the recommendable sizes. For instance, if I use Microsoft
        > Photo Editor, I go to "Image", and then to "Change Size".

        I don't have this in PhotoDraw. I can only drag smaller. You have mentioned
        three ways of reducing file size below:
        (1) pixel size
        (2) dimensions such as inches or cm
        (3) ratio, such as 1/3 size

        The important thing is to keep aspect constant. Aspect is the relation of
        width to height. If you reduce height for example but don't change width then
        your picture will look squashed. If you use ratio then aspect will be
        maintained. If you use pixels or cms then try changing only width or height
        and see if the other dimension will change automatically. Thumbs Plus lets
        you set 'Aspect Fit' to 'both' to accomplish this.

        For my own pages, I use 'big' pictures of no more than 300 x 400 pixels, and
        these could be anywhere from 20 to 60 kbytes. All your thumbnails on the
        webheads pages are 60x70 pixels and range in size from 1.5 to 5 kbytes. To
        get your pictures to that size I cropped the face as much as possible, reduced
        either L or W to its correct dimension, and then cropped the other dimension
        to get it to the correct size.

        > There, I
        > find the units in pixels, inches and cm, well, I never know how to
        > set this. Sometimes I change the pixels and the picture is still too
        > large.Until I try the picture on the webpage I do not know if it will
        > fit there or not. If I use PhotoStudio, it has a reducing feature
        > expressed in figures like 1:1,1:3, etc. I am lost. I heard someone
        > say that a good size for web pictures was 72 pixels by inch. Is this
        > right? If so, How do I get that?
        > I am all ears for advice.

        I believe this is 72 dots per inch. In PhotoDraw there is a compression
        option (high compression gives smaller filesize). In Thumbs Plus you can
        adjust color 'depth' but I don't think you can set dpi.

        Susanne says she thinks gif is most appropriate for web quality. One
        advantage to gif is that you can set a background color to transparent so it
        blends in with your web page background, and another is that you can run gif
        images together to make an animated gif. Still another, or so I have read, is
        that gif is not as lossy as jpeg during processing (meaning that if you alter
        a gif you won't lose quality with each operation as much as you will with
        jpeg). The advice in the article I read was to work in gif and do a final
        save as jpeg. Image software (Thumbs Plus for example) will let you convert
        to and save in whichever format you want. Most web images I encounter are
        either gif or jpeg.

        If anyone can add to this please do.

        Vance
      • dygonza
        Thank you Sus and Vance for your suggestions, I will try tomorrow to see what happens. I am going do download the application Vance suggested to see if I am
        Message 3 of 4 , Mar 2, 2002
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          Thank you Sus and Vance for your suggestions, I will try tomorrow to
          see what happens. I am going do download the application Vance
          suggested to see if I am able to figure out the steps of the
          process.:-)

          Daf

          --- In evonline2002_webheads@y..., Vance Stevens <vstevens@e...>
          wrote:
          > Thanks Dafne for starting the ball rolling on the questions.
          >
          > I've seen Susanne's response and she is correct that dots per inch
          or density
          > of information has much to do with the FILEsize of an image and
          therefore how
          > long it will take to download over the Internet.
          >
          > It's much easier to control the filesize of an image though two
          other means:
          > cropping and resizing.
          >
          > My favorite tool for doing these operations is Thumbs Plus,
          > http://www.cerious.com . Using this tool, you browse your hdd for
          images and
          > click on the thumbs icons to see their thumbnails. You can then
          click on an
          > image to bring it up and drag a box on it to crop it (Edit/Crop),
          or use Image
          > / Rotate & Resize to make the picture smaller.
          >
          > One nice feature of this program is the Options / Preferences
          features. The
          > File List tab for example allows you to display the File Size in
          bytes and
          > Dimensions in pixels of your image. It's very handy to have this
          information
          > right in front of you when viewing images. As Susanne mentioned,
          you want to
          > keep your file sizes down to well below 100 kbytes, in fact below
          50 in most
          > cases, for fast download to your vistors' browsers.
          >
          > dygonza wrote:
          >
          > > Hi Everybody,
          > >
          > > Taking on this week's topic I would like to express my ignorance
          > > about resizing pictures. I have three applications that do the
          work:
          > > Paint, Microsoft Photo Editor and PhotoStudio 2000 (this one came
          > > with my webcam).
          >
          > I've launched Microsoft PhotoDraw 2000 and I can see that I can
          drag the image
          > smaller though I can't specify a filesize as I can with Thumbs Plus.
          >
          > > I have managed to resize my pictures for the
          > > webpage. But I do not know how I have done it. I mean, I start
          trying
          > > until I get a size that fits the available space and is easy to
          > > download, but I do not know how to get a specific size, neither
          know
          > > I which are the recommendable sizes. For instance, if I use
          Microsoft
          > > Photo Editor, I go to "Image", and then to "Change Size".
          >
          > I don't have this in PhotoDraw. I can only drag smaller. You have
          mentioned
          > three ways of reducing file size below:
          > (1) pixel size
          > (2) dimensions such as inches or cm
          > (3) ratio, such as 1/3 size
          >
          > The important thing is to keep aspect constant. Aspect is the
          relation of
          > width to height. If you reduce height for example but don't change
          width then
          > your picture will look squashed. If you use ratio then aspect will
          be
          > maintained. If you use pixels or cms then try changing only width
          or height
          > and see if the other dimension will change automatically. Thumbs
          Plus lets
          > you set 'Aspect Fit' to 'both' to accomplish this.
          >
          > For my own pages, I use 'big' pictures of no more than 300 x 400
          pixels, and
          > these could be anywhere from 20 to 60 kbytes. All your thumbnails
          on the
          > webheads pages are 60x70 pixels and range in size from 1.5 to 5
          kbytes. To
          > get your pictures to that size I cropped the face as much as
          possible, reduced
          > either L or W to its correct dimension, and then cropped the other
          dimension
          > to get it to the correct size.
          >
          > > There, I
          > > find the units in pixels, inches and cm, well, I never know how to
          > > set this. Sometimes I change the pixels and the picture is still
          too
          > > large.Until I try the picture on the webpage I do not know if it
          will
          > > fit there or not. If I use PhotoStudio, it has a reducing feature
          > > expressed in figures like 1:1,1:3, etc. I am lost. I heard someone
          > > say that a good size for web pictures was 72 pixels by inch. Is
          this
          > > right? If so, How do I get that?
          > > I am all ears for advice.
          >
          > I believe this is 72 dots per inch. In PhotoDraw there is a
          compression
          > option (high compression gives smaller filesize). In Thumbs Plus
          you can
          > adjust color 'depth' but I don't think you can set dpi.
          >
          > Susanne says she thinks gif is most appropriate for web quality.
          One
          > advantage to gif is that you can set a background color to
          transparent so it
          > blends in with your web page background, and another is that you
          can run gif
          > images together to make an animated gif. Still another, or so I
          have read, is
          > that gif is not as lossy as jpeg during processing (meaning that if
          you alter
          > a gif you won't lose quality with each operation as much as you
          will with
          > jpeg). The advice in the article I read was to work in gif and do
          a final
          > save as jpeg. Image software (Thumbs Plus for example) will let
          you convert
          > to and save in whichever format you want. Most web images I
          encounter are
          > either gif or jpeg.
          >
          > If anyone can add to this please do.
          >
          > Vance
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