在Skia中将画布原点设置为左下角

#include "include/core/SkCanvas.h"
#include "include/core/SkSurface.h"
#include "include/core/SkImageInfo.h"
#include "include/core/SkRect.h"
#include "include/core/SkColor.h"
#include "include/core/SkPaint.h"

void draw(SkCanvas* canvas) {
    // 创建一个红色的画笔
    SkPaint paint;
    paint.setColor(SK_ColorRED);
    paint.setStyle(SkPaint::kFill_Style);

    // 获取画布的尺寸
    SkRect bounds = canvas->getLocalBounds();

    // 在左下角绘制一个矩形
    canvas->drawRect(SkRect::MakeXYWH(0, bounds.height(), 100, 100), paint);
}

int main() {
    // 创建一个100x100的画布
    const int width = 100;
    const int height = 100;
    SkImageInfo imageInfo = SkImageInfo::Make(width, height, kRGBA_8888_SkColorType, kOpaque_SkAlphaType);
    sk_sp<SkSurface> surface(SkSurface::MakeRaster(imageInfo));
    SkCanvas* canvas = surface->getCanvas();

    // 应用变换，将原点移动到左下角
    canvas->concat(SkMatrix::MakeScale(1, -1)); // 垂直翻转
    canvas->translate(0, -height); // 平移

    // 绘制图形
    draw(canvas);

    // 保存结果到文件（可选）
    sk_sp<SkImage> image(surface->makeImageSnapshot());
    if (image) {
        sk_sp<SkData> data(image->encodeToData(SkEncodedImageFormat::kPNG, 100));
        if (data) {
            SkFILEWStream("output.png").write(data->data(), data->size());
        }
    }

    return 0;
}