2. Förbered dina bilder för webben

Ett av de vanligaste användningsområdena för GIMP är att förbereda bilder för webbplatser. Detta innebär att bilder ska se så bra ut som möjligt medan filstorleken hålls så liten som möjligt. Denna guide visar steg för steg hur du kan skapa små filer med minimal förlust i bildkvalitet.

2.1. Bilder med optimalt förhållande mellan storlek och kvalitet

An optimal image for the web depends upon the image type and the file format. Use JPEG for Photographs because they usually have many colors and great detail. An image with fewer colors, such as a button, icon, or screenshot, is better suited to the PNG format.

  1. First, open the image as usual. I have opened our Wilber as an example image.

    Figur 6.9. Wilber-bilden öppnad i RGBA-läge

    Wilber-bilden öppnad i RGBA-läge

  2. The image is now in RGB mode, with an additional Alpha channel (RGBA). There is usually no need to have an alpha channel for your web image. You can remove the alpha channel by flattening the image.

    A photograph rarely has an alpha channel, so the image will open in RGB mode rather than RGBA mode; and you won't have to remove the alpha channel.

    [Notera] Notera

    If the image has a soft transition into the transparent areas, you should not remove the alpha channel, since the information used for the transition is not be saved in the file. To export an image with transparent areas that do not have a soft transition, (similar to GIF), remove the alpha channel.

  3. After you have flattened the image, export the image in the PNG format for your web site.

[Notera] Notera

You can export your image in the PNG format with the default settings. Always using maximum compression when creating the image. Maximum compression has no effect on image quality or the time required to display the image, but it does take longer to export. A JPEG image, however, loses quality as the compression is increased. If your image is a photograph with lots of colors, you should use jpeg. The main thing is to find the best tradeoff between quality and compression. You can find more information about this topic in Avsnitt 1.2.3, ”Exportera bild som JPEG”.