module FreeImage::Pixels

  1. lib/free-image/modules/pixels.rb

Summary ↑

The Pixel module provides methods that allow you to read, write and work pixel-by-pixel with image data. FreeImage not only can work with standard bitmap data (e.g. 1-, 4-, 8-, 16-, 24- and 32-bit) but also with scientific data such as 16-bit greyscale images, or images made up of long, double or complex values (often used in signal and image processing algorithms).

The FreeImage coordinate system is upside down relative to usual graphics conventions. Thus, the scanlines are stored upside down, with the first scan in memory being the bottommost scan in the image.

For additional information, please refer to the FreeImage::Scanline documentation.

Public Instance methods

bits ()

Returns the data-bits of the bitmap. It is up to you to interpret these bytes correctly, according to the results of FreeImage::Information#bits_per_pixel, FreeImage::Information#red_mask, FreeImage::Information#green_mask and FreeImage::Information#blue_mask.

If the bitmap does not contain pixel data (see FreeImage::Information#has_pixels), nil will be returned.

For a performance reason, the address returned by FreeImage_GetBits is aligned on a 16 bytes alignment boundary

[show source] 
# File lib/free-image/modules/pixels.rb, line 45
def bits
  ptr = FreeImage.FreeImage_GetBits(self)
  FreeImage.check_last_error
  ptr.read_string
end
pixel_color (x, y)

Gets the pixel color of a 16-, 24- or 32-bit image at the specified coordinate.

Parameters ↑

x

The pixel position in horizontal direction

y

The pixel position in vertical direction.

[show source] 
# File lib/free-image/modules/pixels.rb, line 113
def pixel_color(x, y)
  color = RGBQuad.new
  result = FreeImage.FreeImage_GetPixelColor(self, x, y, color)
  FreeImage.check_last_error
  result ? color : nil
end
pixel_index (x, y)

Gets the pixel index of a palettized image at the specified coordinate.

Parameters ↑

x

The pixel position in horizontal direction

y

The pixel position in vertical direction.

[show source] 
# File lib/free-image/modules/pixels.rb, line 71
def pixel_index(x, y)
  byte_type = FreeImage.find_type(:byte)
  ptr = FFI::MemoryPointer.new(byte_type)
  result = FreeImage.FreeImage_GetPixelIndex(self, x, y, ptr)
  FreeImage.check_last_error
  return nil unless result
  
  data = ptr.read_bytes(byte_type.size)
  if byte_type.size == 1
    data.ord
  else
    data
  end
end
scanline (index)

Returns the requested row of image data as a FreeImage::Scanline instance.

If the bitmap does not contain pixel data (see FreeImage::Information#has_pixels), nil will be returned.

[show source] 
# File lib/free-image/modules/pixels.rb, line 55
def scanline(index)
  unless (0...self.height).include?(index)
    raise(RangeError, "Index must be between 0 and #{self.height - 1}")
  end
  ptr = FreeImage.FreeImage_GetScanLine(self, index)
  FreeImage.check_last_error

  ptr ? Scanline.new(self, index, ptr) : nil
end
set_pixel_color (x, y, color)

Sets the pixel color of a 16-, 24- or 32-bit image at the specified coordinate.

Parameters ↑

x

The pixel position in horizontal direction

y

The pixel position in vertical direction.

color

The new color as a RGBAQuad instance.

The function returns true on success and false otherwise.

[show source] 
# File lib/free-image/modules/pixels.rb, line 129
def set_pixel_color(x, y, color)
  result = FreeImage.FreeImage_SetPixelColor(self, x, y, color)
  FreeImage.check_last_error
  result
end
set_pixel_index (x, y, index)

Sets the pixel index of a palettized image at the specified coordinate.

Parameters ↑

x

The pixel position in horizontal direction

y

The pixel position in vertical direction.

The function returns true on success and false otherwise.

[show source] 
# File lib/free-image/modules/pixels.rb, line 94
def set_pixel_index(x, y, index)
  byte_type = FreeImage.find_type(:byte)
  ptr = FFI::MemoryPointer.new(byte_type.size)
  if byte_type.size == 1
    ptr.put_bytes(0, index.chr, 0, byte_type.size)
  else
    ptr.put_bytes(0, index.to_s, 0, byte_type.size)
  end
  result = FreeImage.FreeImage_SetPixelIndex(self, x, y, ptr)
  FreeImage.check_last_error
  result
end