Strange problem about conversion between GDI+ to GDI: Bitmap and HBitmap

bitmapgdi+hbitmap

I want to convert gdi+ Bitmap into gdi object HBitmap.

I am using the following method:

   Bitmap* img = new Bitmap(XXX);
            // lots of codes...
    HBITMAP temp;
    Color color;
    img->GetHBITMAP(color, &temp);

the img object is drawing on a dialog.
when this part of method is called, strange thing happens!
the img displaying in the window changed!
It become a bit clearer or sharper.
My question is what happens?

Best Solution

The bitmap pixel format may be the reason. Do you specify it explicitly in the Bitmap constructor?

Gdiplus::Bitmap bmp(WIDTH, HEIGHT, PixelFormat24bppRGB);

Try making sure that all the pixel formats you use are the same.

Another reason may be the differences in Gdiplus::Graphics interpolation modes in your code. That attribute determines how the images are resized, how the lines are drawn, etc.

m_pViewPortImage = new Gdiplus::Bitmap(
    observedWidth,
    observedHeight,
    PixelFormat24bppRGB
);

Gdiplus::Graphics gr(m_pViewPortImage);
gr.SetInterpolationMode(Gdiplus::InterpolationModeHighQualityBicubic);

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Android – Strange OutOfMemory issue while loading an image to a Bitmap object

To fix the OutOfMemory error, you should do something like this:

BitmapFactory.Options options = new BitmapFactory.Options();
options.inSampleSize = 8;
Bitmap preview_bitmap = BitmapFactory.decodeStream(is, null, options);

This inSampleSize option reduces memory consumption.

Here's a complete method. First it reads image size without decoding the content itself. Then it finds the best inSampleSize value, it should be a power of 2, and finally the image is decoded.

// Decodes image and scales it to reduce memory consumption
private Bitmap decodeFile(File f) {
    try {
        // Decode image size
        BitmapFactory.Options o = new BitmapFactory.Options();
        o.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(new FileInputStream(f), null, o);

        // The new size we want to scale to
        final int REQUIRED_SIZE=70;

        // Find the correct scale value. It should be the power of 2.
        int scale = 1;
        while(o.outWidth / scale / 2 >= REQUIRED_SIZE && 
              o.outHeight / scale / 2 >= REQUIRED_SIZE) {
            scale *= 2;
        }

        // Decode with inSampleSize
        BitmapFactory.Options o2 = new BitmapFactory.Options();
        o2.inSampleSize = scale;
        return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
    } catch (FileNotFoundException e) {}
    return null;
}

A strange Problem about gdi+ bitmap!

Did you call GdiplusStartup before creating the Bitmap?

Best Solution

Related Solutions

Android – Strange OutOfMemory issue while loading an image to a Bitmap object

A strange Problem about gdi+ bitmap!

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