how can I change color "automatically"

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Scott User Profile View All Posts by User View Thanks		#1 Posted : Friday, May 19, 2006 7:07:42 AM(UTC)
Rank: Member Groups: Member Joined: 9/13/2004(UTC) Posts: 4		I need to take a black and white image that is uploaded and convert it to red and white, or blue and white, etc. The color will be one of a few (5 or 6) and I need to do this basically without user intervention. Is there an easy way to process the image to apply the color in place of the black in the image? The interface I have is so incredibly simple that the user is just "approving" uploaded images for copyright and objectional material, so I want to apply the color in VB6 code in the background when I open the file. Then it will be saved for printing with the color instead of the black. And ideas or help would be greatly appreciated?

Andrew User Profile View All Posts by User View Thanks		#2 Posted : Friday, May 19, 2006 11:43:35 AM(UTC)
Rank: Advanced Member Groups: Member, Administration Joined: 8/2/2003(UTC) Posts: 876 Thanks: 2 times Was thanked: 27 time(s) in 27 post(s)		If you work with indexed image (1-bit, 4-bit, or non-grayscale 8-bit), you can just replace an appropriate color in the palette. Even if you use 24-bit RGB bitmaps, you can convert them to 8-bit indexed bitmap. Since you said that actually the image contains only few colors, it will not make any problems (moreover, it will save some memory). Code: `Dim objBmp As New Bitmap objBmp.LoadFromFile "c:\image.bmp" If Not objBmp.Data.IsIndexed Then objBmp.Data.ConvertTo8bppIndexed DitheringTypeNone End If Dim intBlackColorIndex As Integer intBlackColorIndex = objBmp.Data.Palette.FindNearestIndex(ColorBlack) objBmp.Data.Palette(intBlackColorIndex) = ColorBlue objBmp.SaveToFile "c:\result.bmp"` FindNearestIndex method works quite slowly (which is noticeable for large palettes). If you are sure that the color you replace is presented in the bitmap, you can just iterate the palette entries and replace an appropriate ones: Code: `Dim I As Integer For I = 0 To objBmp.Data.Palette.Count - 1 If objBmp.Data.Palette(I) = ColorBlack Then objBmp.Data.Palette(I) = ColorBlue End If Next` Hope this helps. Edited by user Thursday, December 20, 2007 4:33:13 PM(UTC) \| Reason: Not specified

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