CPJAImage - Yet another image drawing class

• Download source files - 8 Kb
• Download demo project - 50 Kb

Updates

Aug 23, 2003 - Fixed transparent drawing bug

Introduction

After I wrote my CFileEditCtrl edit control, I got a request to place an image on the browse button, and then another request to make the control flat and hot to the mouse. That was becoming quite a task, searching on this site and www.codeguru.com for drawing code that would draw images, either bitmaps or icons, either normally or transparently, grey-scaled or disabled, possibly stretched or at least centered on the button. So after finding some code that solved one bit or another (but not quite the way I wanted), I put them together, filled in the pieces that were missing and came up with the CPJAImage class. While the reason I wrote the class was for the browse button, I thought it was a shame not to share it with you as yet another separate image rendering class.

Acknowledgments

Jean-Edouard Lachand-Robert for his DitherBlt() function.

Paul Reynolds for the "True Mask" transparency function.

Zafir Anjum and Guy Gascoigne for their greyscale algorithm.

Using the CPJAImage class

The first step is to include the PJAImage.h and PJAImage.cpp files in your project. Then after you have loaded or created your bitmap or icon object in the normal fashion, select it into the CPJAImage object using the SetImage() function.

CBitmap Bitmap;
Bitmap.LoadBitmap(IDB_BITMAP1);
CPJAImage PJAImage;
PJAImage.SetImage(Bitmap, PJAI_BITMAP);

Then when you are ready to draw the image, use the DrawImage() function to draw the image onto the given device context.

PJAImage.DrawImage(pDC, left, top, width, height, DrawFlags);

The drawing flags you specify in the DrawImage() function determine how the image is drawn.

User functions

CPJAImage::CPJAImage()

The class constructor creates an empty CPJAImage object.

CPJAImage::~CPJAImage()

The class destructor destroys the image handle

void CPJAImage::DrawImage(CDC *pToDC, int x, int y, int w, int h, DWORD DrawFlags = 0)

The DrawImage() does the actual drawing.

Parameters

Flags used in the DrawFlags parameter

CSize CPJAImage::GetSize()

Returns a CSize object that contains the size of the image currently contained in the CPJAImage.

BOOL CPJAImage::SetImage(HANDLE hImage, DWORD Flags)

Selects the supplied image into the CPJAImage object. Returns TRUE if the supplied image was successfully selected, FALSE if not.

Parameters

Flags used by the SetImage() function

COLORREF CPJAImage::SetTransparentColor(COLORREF clr = CLR_DEFAULT)

Sets the color to be used as the transparent color for the bitmap image. Returns the previous transparent color. If CLR_DEFAULT (0xFF000000) is set as the transparent color, the color of the pixel at the top left corner ( GetPixel (0, 0) ) is used as the transparent color.

Parameters

Demonstration Application

Be sure to check out the demo app to see the CPJAImage class in action. While the demo has a preloaded image in it, you can drag 'n drop your favorite picture files ( *.ico, *.bmp, *.jpg, or *.gif ) onto the demo app.

To change the transparent color, click the Set Color button, and then use the mouse to select the color from the picture displayed.

Enjoy!