[2.0] Saving transparent images.

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

Code:

---

        /// <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:

Code:

---

        /// <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.

Code:

---

        /// <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

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?

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.

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.

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

=(

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

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

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

Cheers!
//Zolomon