Using Skia in Windows

[nrc]

Hi, what is the best way to use Skia in a toy native Windows application? I've built Skia using Visual Studio and can use it as a lib, but I don't know how to get from an SkCanvas to the screen. The only advice from the web was to use an SkPlatformCanvas (or SkPlatformCanvasPaint) instead of an SkCanvas, but these classes seem to have disappeared.

Put another way, what is the Skia equivalent to something like

            cairo_surface_t* surface = cairo_win32_surface_create(hdc);
            cairo_t* ctxt = cairo_create(surface);

in Cairo?

Thanks, Nick

[Chandramouli Sanchi]

Hi,

 

Plz try as below:

 

#include "SkBitmap.h"

#include "SkDevice.h"

#include "SkPaint.h"

#include "SkRect.h"

#include <cairo.h>  

int main()

 {

SkBitmap bitmap;

bitmap.setConfig(SkBitmap::kARGB_8888_Config, 100, 100);

bitmap.allocPixels();

SkDevice device(bitmap);

SkCanvas canvas(&device);

SkPaint paint;

SkRect r;  

paint.setARGB(255, 255, 255, 255);

r.set(10, 10, 20, 20);

canvas.drawRect(r, paint);  

 {

 SkAutoLockPixels image_lock(bitmap);

 cairo_surface_t* surface = cairo_image_surface_create_for_data( (unsigned char*)bitmap.getPixels(), CAIRO_FORMAT_ARGB32, bitmap.width(), bitmap.height(), bitmap.rowBytes());

 cairo_surface_write_to_png(surface, "snapshot.png");

 cairo_surface_destroy(surface);

 }

  return 0;

}

 

 

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[Mike Reed]

SkOSWindow_win.cpp does this, either with SetDIBitsToDevice() or using opengl.

BITMAPINFO bmi;
memset(&bmi, 0, sizeof(bmi));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = bitmap.width();
bmi.bmiHeader.biHeight = -bitmap.height(); // top-down image
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biSizeImage = 0;

//
// Do the SetDIBitsToDevice.
//
// TODO(wjmaclean):
// Fix this call to handle SkBitmaps that have rowBytes != width,
// i.e. may have padding at the end of lines. The SkASSERT below
// may be ignored by builds, and the only obviously safe option
// seems to be to copy the bitmap to a temporary (contiguous)
// buffer before passing to SetDIBitsToDevice().
SkASSERT(bitmap.width() * bitmap.bytesPerPixel() == bitmap.rowBytes());
bitmap.lockPixels();
int iRet = SetDIBitsToDevice(hdc,
0, 0,
bitmap.width(), bitmap.height(),
0, 0,
0, bitmap.height(),
bitmap.getPixels(),
&bmi,
DIB_RGB_COLORS);
bitmap.unlockPixels();

[Edvardas Ščerbavičius]

Hi,

I am using code from Chromium(PlatformCanvasPaint) to build native Windows application.

Here you can find instructions how to build Skia .dll and sample app:

https://github.com/vosvos/skia-win32-dll

Sample application:

https://github.com/vosvos/skia-win32-dll/blob/master/win32_app/skia_app.cpp

Edvardas

[nrc]

Thanks Mike, that is exactly what I was after!

[nrc]

Thanks Edvardas! I prefer to use the Skia library as a stand alone, without the Chromium stuff, but you instructions were useful to help get everything built :-)