Scaling sample:
Unlike traditional scaling of images, where every n’th pixel is sampled and copied to the
result image, this template provides much more accurate image scaling features.
It takes a buffer of RGB values (as COLORREFs) and creates another buffer with new dimensions. The input / output buffers are sequential pixels (not compressed) compatible with the format used in 24-bit DIBs.
The template is instantiated with a specific filter. The filter determines the quality of
the output image. Different basic filters are supplied with this template and additional filters can be easily added.
Major features:
- Provides professional quality image scaling.
- Code is optimized for image quality, not speed.
- Supports various image filters:
- Box filter.
- Bilinear filter.
- Gaussian filter.
- Hamming filter.
- Blackman filter.
- …New filters can be easily added.
- Supports both magnification and minification.
- Does not force aspect ratio limitations. e.g. an image can be magnified horizontally and minified vertically.
- Supports 24-bit images. With little change can support other image formats / depths.
- Template based – no need for libraries, DLLs etc. No linkage problems.
How to use the scaling template:
Assuming you have a non-compressed true-color 24-bit DIB in memory (the bits array is pointed by m_pBits), where the original bitmap width is m_dwWidth and height is m_dwHeight.
Your code should look something like this:
#include <2PassScale.h>
…
void CMyDIB::ScaleTo (DWORD dwNewWidth, DWORD dwNewHeight)
{
C2PassScale <CBilinearFilter> ScaleEngine;
COLORREF *pOldBitmap = m_pBits;
m_pBits = ScaleEngine.AllocAndScale ( m_pBits,
m_dwWidth,
m_dwHeight,
dwNewWidth,
dwNewHeight
);
if (NULL == m_pBits)
{
//
// Handle errors here
//
}
m_dwWidth = dwNewWidth;
m_dwHeight = dwNewHeight;
delete pOldBitmap;
}
//
// Alternatively, if you already have a pre-allocated destination buffer
// in the new size you can call ScaleEngine.Scale (…) and give it that buffer
//