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| Josef Wainz |
how can i improve the quality of a saved gif?
the code below opens 3 gif files and merges them into 1 by using a
bitmap. when i convert the bitmap back to gif the image quality is
less than the gif quality i started with. i save it 2 ways, but it
doesn't seem to make a difference.
any suggestions.
//create images from files
Image map = Image.FromFile("C:\\Projects\\MapGen\\bin\\Debug\\Images\\Terminal463DrivetimeZones.gif",
true);
Image logo = Image.FromFile("C:\\Projects\\MapGen\\ctilogo2.gif",
true);
Image legend = Image.FromFile("C:\\Projects\\MapGen\\Legend\\Legend.gif",
true);
//create bitmap
Bitmap bm = new Bitmap(755, 480, PixelFormat.Format64bppPArgb);
//draw images onto bitmap
Graphics g = Graphics.FromImage(bm);
g.DrawImage(map, 1, 1);
g.DrawImage(legend, 10, 440, 300, 25);
g.DrawImage(logo, 380, 430, 90, 35);
//save as gif with encoderparameter
EncoderParameters eps = new EncoderParameters(1);
eps.Param[0] = new EncoderParameter( Encoder.Quality, 75);
ImageCodecInfo ici = GetEncoderInfo("image/gif");
bm.Save("C:\\Projects\\MapGen\\Brand\\BrandNew.gif", ici, eps);
//save as gif
bm.Save("C:\\Projects\\MapGen\\Brand\\Brand.gif", ImageFormat.Gif);
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| John Hornick [MS] (VIP) |
Hi,
[Original message clipped]
meZones.gif",
[Original message clipped]
GIF is not a lossy compression. It isn't the quality that's bad, it's the
color table. GDI+ will always convert your image to 8bpp from 32bpp using
a default "rainbow" palette. (btw, there's no need to try to use 64bpp.
you might as well stick with 32bpp unless you have some reason to use 64.)
Your image looks bad because it's being dithered into a stock selection
of colors, rather than an optimal collection of colors.
To get a better looking image, you'll need to compose an optimal palette
with which to save the image. See the following for more information:
Q318343 INFO: GDI+ GIF Files Are Saved Using the 8-Bpp Format
Q315780 HOWTO: Save a .gif File with a New Color Table By Using GDI+
Q319061 HOW TO: Save a .gif File with a New Color Table By Using Visual C#
Q319591 HOW TO: Save a GIF with a New Color Table By Using Visual Basic.NET
Those articles tell you how to save a GIF with a color table of your
choice. All that's left is to choose a color table. Look for median cut
palette or octree palette or popularity palette on the web or in your
favorite computer graphics books.
Thanks,
- John
Microsoft Developer Support
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