[2.0] Saving transparent images.

[Fromethius]

I'm using this method to help achieve transparency in a bitmap/image:

        /// <summary>
        /// Enables semi-transparency in an image.
        /// </summary>
        /// <param name="transparency">Transparency value between 0.0 and 1.0.</param>
        /// <returns>ImageAttributes.</returns>
        private static ImageAttributes GetTransparentAttributes(float transparency)
        {
            if (transparency < 0 || transparency > 1)
            {
                throw new ArgumentOutOfRangeException("Value must be between 0.0 and 1.0.");
            }

            ColorMatrix colorMatrix = new ColorMatrix(
            new float[][] { 
            new float[] {1, 0, 0, 0, 0},
            new float[] {0, 1, 0, 0, 0},
            new float[] {0, 0, 1, 0, 0},
            new float[] {0, 0, 0, transparency, 0},
            new float[] {0, 0, 0, 0, 1}});

            ImageAttributes imageAttributes = new ImageAttributes();
            imageAttributes.SetColorMatrix(colorMatrix);

            return imageAttributes;
        }

I use this method to actually create the transparent bitmap:

        /// <summary>
        /// Creates an image based on the image and transparency given.
        /// </summary>
        /// <param name="directory">The directory of the bitmap to be made into a cursor.</param>
        /// <param name="transparency">Transparency value between 0.0 and 1.0.</param>
        /// <returns>Image.</returns>
        private static Image Create(string directory, float transparency)
        {
            Bitmap sourceBitmap = new Bitmap(directory);
            Bitmap tempBitmap = new Bitmap(sourceBitmap.Width, sourceBitmap.Height);
            Graphics myGraphics = Graphics.FromImage(tempBitmap);
            ImageAttributes imageAttributes = GetTransparentAttributes(transparency);

            myGraphics.DrawImage(sourceBitmap, new Rectangle(0, 0, tempBitmap.Width, tempBitmap.Height), 0, 0, tempBitmap.Width, tempBitmap.Height, GraphicsUnit.Pixel, imageAttributes);

            return tempBitmap;
        }

Finally, I use this method to save the transparent image to a directory.

        /// <summary>
        /// Saves an image with a different file format.
        /// </summary>
        /// <param name="directory">The directory of the image to save as a different file format.</param>
        /// <param name="extension">The new extension (with a leading period).</param>
        public static void Save(string inputDirectory, string outputDirectory, string newExtension, float newTransparency)
        {
            Image image = Create(inputDirectory, newTransparency);
            image.Save(Path.ChangeExtension(outputDirectory, newExtension));
        }

However, when opening the image in Microsoft Paint or any other photo editing programs, the image is either not transparent at all, corrupt, or just normal. I think this is happening because BMP's cannot be saved as transparent, so I am asking if there is a way to save the pixels of the transparent image so that it will look transparent even if the image isn't transprent. It's a bit hard to word that :P

I want to save the transparent image in a bitmap. I know it's got to be possible. Does anyone know how?

Thanks

[wossname]

MS paint is no indication of transparency. Don't rely on it. Use Gimp or something else.

Why can't you save it as a PNG instead?

[Fromethius]

Because the third parameter for SystemParametersInfo takes only filenames of bitmap files. If I supply some random bitmap I made in paint as the parameter, it works fine, but if I supply the file made via my program, it doesn't do anything. Apparently the image is either corrupt, unreadable, or BMP's do not support transparency or something.

[Phill64]

That's right, bitmaps don't support transparency.

I mean, yes, as you said it's "possible" the format technically *could*, but I've never seen a transparent bitmap, have you? You should save as PNG as the cat has suggested.

[Fromethius]

Wouldn't really work =/ The API call I'm trying to use requires the filename of a bitmap file.

=(

[Zolomon]

Hello!

I know how to convert images to BMP. I don't have the functions at my current place but I'll gladly post them when I get home! I'm currently writing a WallPaper changer application and I found a solution to this problem (that is, how to convert an image to BMP so you can use it with SystemParametersInfo())

Cheers!
//Zolomon

[Fromethius]

Haha! Exactly what I need and exactly what I'm doing. Thanks.

[Zolomon]

I'll post this link for you, you'll learn a lot more from there!

Cheers!
//Zolomon