ios - 替换 CGBitmapContext 中的特定颜色

Question

如何替换 CGBitmapContext 中已绘制的特定颜色(RGB 值)？

有什么简单的方法吗？

提前致谢。

Answer 1

您需要通过执行以下操作来获得指向像素和有关其格式的信息的指针:

// This assumes the data is RGBA format, 8-bits per channel. 
// You'll need to verify that by calling CGBitmapContextGetBitsPerPixel (), etc.
typedef struct RGBA8 {
    UInt8 red;
    UInt8 green;
    UInt8 blue;
    UInt8 alpha;
} RGBA8;

RGBA8* pixels = CGBitmapContextGetData (context);
UInt32 height = CGBitmapContextGetHeight (context);
UInt32 width = CGBitmapContextGetWidth (context);
UInt32 rowBytes = CGBitmapContextGetBytesPerRow (context);
UInt32 x, y;
for (y = 0; y < height; y++)
{
    RGBA8* currentRow = (RGBA8*)((UInt8*)pixels + y * rowBytes);
    for (x = 0; x < width; x++)
    {
        if ((currentRow->red == replaceRed) && (currentRow->green == replaceGreen) &&
            (currentRow->blue == replaceBlue) && (currentRow->alpha == replaceAlpha))
        {
            currentRow->red = newRed;
            currentRow->green = newGreen;
            currentRow->blue = newBlue;
            currentRow->alpha = newAlpha;
        }
        currentRow++;
    }
}