我正在使用双线性技术重新调整图像大小,参考了这里的方法,但我只看到一个黑色图像。首先,我使用LodePNG对我的图像进行解码,并将像素存储在
现在我有一个来自上面指定链接的函数,它应该进行插值:
vector<unsigned char>
变量中。它说它们是以RGBARGBA格式存储的,但当我尝试将图像应用于X11窗口时,我意识到它们是以BGRABGRA格式存储的。我不知道是X11 API改变了顺序还是LodePNG解码器的问题。无论如何,在任何操作之前,我都会将BGR转换为RGB:// Here is where I have the pixels stored
vector<unsigned char> Image;
// Converting BGRA to RGBA, or vice-versa, I don't know, but it's how it is shown
// correctly on the window
unsigned char red, blue;
unsigned int i;
for(i=0; i<Image.size(); i+=4)
{
red = Image[i + 2];
blue = Image[i];
Image[i] = red;
Image[i + 2] = blue;
}
现在,我正在尝试在将图像应用于窗口之前更改其大小。大小应为窗口的大小(拉伸它)。 我首先尝试将RGBA转换为整数值,如下所示:
vector<int> IntImage;
for(unsigned i=0; i<Image.size(); i+=4)
{
IData.push_back(256*256*this->Data[i+2] + 256*this->Data[i+1] + this->Data[i]);
}
现在我有一个来自上面指定链接的函数,它应该进行插值:
vector<int> resizeBilinear(vector<int> pixels, int w, int h, int w2, int h2) {
vector<int> temp(w2 * h2);
int a, b, c, d, x, y, index ;
float x_ratio = ((float)(w-1))/w2 ;
float y_ratio = ((float)(h-1))/h2 ;
float x_diff, y_diff, blue, red, green ;
for (int i=0;i<h2;i++) {
for (int j=0;j<w2;j++) {
x = (int)(x_ratio * j) ;
y = (int)(y_ratio * i) ;
x_diff = (x_ratio * j) - x ;
y_diff = (y_ratio * i) - y ;
index = (y*w+x) ;
a = pixels[index] ;
b = pixels[index+1] ;
c = pixels[index+w] ;
d = pixels[index+w+1] ;
// blue element
// Yb = Ab(1-w)(1-h) + Bb(w)(1-h) + Cb(h)(1-w) + Db(wh)
blue = (a&0xff)*(1-x_diff)*(1-y_diff) + (b&0xff)*(x_diff)*(1-y_diff) +
(c&0xff)*(y_diff)*(1-x_diff) + (d&0xff)*(x_diff*y_diff);
// green element
// Yg = Ag(1-w)(1-h) + Bg(w)(1-h) + Cg(h)(1-w) + Dg(wh)
green = ((a>>8)&0xff)*(1-x_diff)*(1-y_diff) + ((b>>8)&0xff)*(x_diff)*(1-y_diff) +
((c>>8)&0xff)*(y_diff)*(1-x_diff) + ((d>>8)&0xff)*(x_diff*y_diff);
// red element
// Yr = Ar(1-w)(1-h) + Br(w)(1-h) + Cr(h)(1-w) + Dr(wh)
red = ((a>>16)&0xff)*(1-x_diff)*(1-y_diff) + ((b>>16)&0xff)*(x_diff)*(1-y_diff) +
((c>>16)&0xff)*(y_diff)*(1-x_diff) + ((d>>16)&0xff)*(x_diff*y_diff);
temp.push_back(
((((int)red)<<16)&0xff0000) |
((((int)green)<<8)&0xff00) |
((int)blue) |
0xff); // hardcode alpha ;
}
}
return temp;
}
我是这样使用它的:
vector<int> NewImage = resizeBilinear(IntData, image_width, image_height, window_width, window_height);
这段代码应该返回调整大小后图像的RGBA向量。现在,我要从整数格式转换回RGBA格式。
Image.clear();
for(unsigned i=0; i<NewImage.size(); i++)
{
Image.push_back(NewImage[i] & 255);
Image.push_back((NewImage[i] >> 8) & 255);
Image.push_back((NewImage[i] >> 16) & 255);
Image.push_back(0xff);
}
我得到的是一个黑色窗口(默认背景颜色),所以我不知道我缺少了什么。如果我注释掉获取新图像并只将IntImage
转换回RGBA的行,我会得到正确的值,因此我不知道是否是混乱的RGBA/int <> int/RGBA引起的。现在我感到很困惑。我知道这可以被优化/简化,但现在我只想让它工作。