default to bmp file to avoid encoder error

[MaverickTse]

Depending on OpenCV build customization, encoding to formats other than BMP may not work.

[MaverickTse]

also convert your Mat to CV_8UC3 at some point before imwrite() if you're not writing to PNG. BTW, do you need transparency at all?

[yumetodo]

do you need transparency at all?

いいえ。このソフトは透過情報についての処理をする予定はありません。(画面キャプチャーをする時透過情報は不要)

convert your Mat to CV_8UC3

cv::Mat::convertToが(PNG以外には)必要ということですか？つまり

namespace converter {
    cv::Mat BITMAP_to_cv_Mat(const BITMAP & img) {
        cv::Mat re(img.bmHeight, img.bmWidth, CV_8UC4, img.bmBits,img.bmWidthBytes);
        re.convertTo(re, CV_8UC3);
        cv::flip(re, re, 0);//上下反転
        return re;
    }
 }

ということ？(pngの判定を除けば)

[MaverickTse]

yes. but in-place format conversion can be dangerous.

[yumetodo]

in-place format conversionとは？ memmove関数みたいな用途(コピー元のメモリー領域とコピー先のメモリー領域が重なっている)のメモリーコピのことですか？

[MaverickTse]

in-place conversion: the converted object occupies the same memory space as the source. but since you are working on a memory block allocated by Windows GDI, you can't guarantee Windows won't touch that memory block. In addition, Mat::convertTo() is a generalized function. To make it works on a variety of format, I bet it copies to a temporary space if it can't find one. In the case of CV_8UC4 → CV_8UC3, it involve shifting bytes, but what if CV_8UC3 → CV_32FC3 ? It MUST allocate a new memory block or will run into access violation. In the end, you can't run away from at least a single new memory allocation. So why not make a copy which we have complete control?

[yumetodo]

How about this code?

namespace converter {
    cv::Mat BITMAP_to_cv_Mat(const BITMAP & img) {
        cv::Mat re;
        cv::Mat(img.bmHeight, img.bmWidth, CV_8UC4, img.bmBits,img.bmWidthBytes).convertTo(re, CV_8UC3);
        cv::flip(re, re, 0);//上下反転
        return re;
    }
 }

[MaverickTse]

cv::Mat src(img.bmHeight, img.bmWidth, CV_8UC4, img.bmBits,img.bmWidthBytes); //no copying here
cv::Mat re;
src.convertTo(re, CV_8UC3); //copy and restructure once here
cv::flip(re, re, 0);
return re;

[yumetodo]

reject. コメントで出た別の方法で修正済み

1

https://github.com/yumetodo/Scatto_continuo_v3/commit/f26c18c7728d991f03b3fe1167b91899f9e7621d