BitmapGrayscale procedure
Converts a bitmap to grayscale taking filtering parameters into account.
Declaration
procedure BitmapGrayscale(ABitmap: TCustomBitmap; RedFilter: Single;
GreenFilter: Single; BlueFilter: Single)Arguments
ABitmap | Bitmap with the image data converted to grayscale in the routine. |
RedFilter | Weighting factor for the contribution of the Red color component to the final grayscale image. It multiplies to the value of the Red component of each pixel and thus controls the contribution of the Red color channel to the resulting image. Having RedFilter = 0, for example, results in grayscale shades in which all parts with Red color components are rendered darker. |
GreenFilter | Weighting factor for the contribution of the Green color component to the final grayscale image. It multiplies to the value of the Green component of each pixel and thus controls the contribution of the Green color channel to the resulting image. Having GreenFilter = 0, for example, results in grayscale shades in which all parts with Green color components are rendered darker. |
BlueFilter | Weighting factor for the contribution of the Blue color component to the final grayscale image. It multiplies to the value of the Blue component of each pixel and thus controls the contribution of the Blue color channel to the resulting image. Having BlueFilter = 0, for example, results in grayscale shades in which all parts with Blue color components are rendered darker. |
Description
BitmapGrayscale is a procedure used to convert the specified
bitmap image to a grayscale image. It calculates the weighted average of the
RGB (Red, Green, Blue) color components of each pixel in the bitmap and
assigns it to each color component. Weighting is done by multiplication of
the RGB values with the corresponding filter factors in the RedFilter,
GreenFilter and BlueFilter arguments. The end result is an image where the
original colors are converted to various shades of gray.
ABitmap is the
TCustomBitmap instance with the original
image data.
RedFilter,
GreenFilter and
BlueFilter are
multipliers (data type: single) for the red, green, blue color components of
each pixel when the average value of the three color components is
calculated. Usually these factors are between 0.0 and 1.0 and are selected to
suppress or enhance the contribution of the corresponding color channel to
the overall grayscale value. The combination 0.30, 0.59, 0.11 for the red,
green and blue components, respectively, is often chosen because it matches
the sensitivity of the human eye and thus results in a visual brightness
impression like in the original color image.
Example Usage:
BitmapGrayscale(Image1.Picture.Bitmap, 0.30, 0.59, 0.11); // Neutral filter BitmapGrayscale(Image1.Picture.Bitmap, 1.00, 0.00, 0.00); // Red filter BitmapGrayscale(Image1.Picture.Bitmap, 0.00, 1.00, 0.00); // Green filter BitmapGrayscale(Image1.Picture.Bitmap, 0.00, 0.00, 1.00); // Blue filter BitmapGrayscale(Image1.Picture.Bitmap, 0.00, 0.50, 0.50); // Cyan filter BitmapGrayscale(Image1.Picture.Bitmap, 0.50, 0.00, 0.50); // Magenta filter BitmapGrayscale(Image1.Picture.Bitmap, 0.50, 0.50, 0.00); // Yellow filter
See also
An experiment, built from development snapshots. Not the official Free Pascal or Lazarus documentation.