是否有可能以編程方式更改圖像的顏色？

Question

我正在使用具有不同主題顏色的應用程序，但我不想在項目中擁有太多的圖像資源（基本上不希望項目尺寸太大），是否可以使用一個圖像但不同的顏色？

謝謝！

Answer 1

我與馬特同意，你應該檢查CIFilter爲未來的圖像修改。但如果你正在尋找一個快速的代碼示例，下面是我如何做到這一點。工作對我來說相當不錯，只需要像這樣調用：

[self useColor:[UIColor redColor] forImage:WHATEVER_IMAGE]; 

- (UIImage *)useColor:(UIColor *)color forImage:(UIImage *)image 
{ 
    if(!color) 
     return image; 

    NSUInteger width = CGImageGetWidth([image CGImage]); 
    NSUInteger height = CGImageGetHeight([image CGImage]); 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    NSUInteger bytesPerPixel = 4; 
    NSUInteger bytesPerRow = bytesPerPixel * width; 
    NSUInteger bitsPerComponent = 8; 
    NSUInteger bitmapByteCount = bytesPerRow * height; 

    unsigned char *rawData = (unsigned char*) calloc(bitmapByteCount, sizeof(unsigned char)); 

    CGContextRef context = CGBitmapContextCreate(rawData, width, height, 
              bitsPerComponent, bytesPerRow, colorSpace, 
              kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); 
    CGColorSpaceRelease(colorSpace); 

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), [image CGImage]); 

    CGColorRef cgColor = [color CGColor]; 
    const CGFloat *components = CGColorGetComponents(cgColor); 
    float r = components[0] * 255.0; 
    float g = components[1] * 255.0; 
    float b = components[2] * 255.0; 
    //float a = components[3]; // not needed 

    int byteIndex = 0; 

    while (byteIndex < bitmapByteCount) 
    { 
     int oldR = rawData[byteIndex]; 
     int oldG = rawData[byteIndex + 1]; 
     int oldB = rawData[byteIndex + 2]; 
     int oldA = rawData[byteIndex + 3]; 
     if(oldR != 0 || oldG != 0 || oldB != 0 || oldA != 0) 
     { 
      rawData[byteIndex] = r; 
      rawData[byteIndex + 1] = g; 
      rawData[byteIndex + 2] = b; 
     } 

     byteIndex += 4; 
    } 

    UIImage *result = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context) scale:image.scale orientation:image.imageOrientation]; 

    CGContextRelease(context); 
    free(rawData); 

    return result; 
} 

Answer 2

您可以使用CIFilter以編程方式以有趣的方式修改圖像的顏色，如果這就是您要求的。

漫步通過目錄... https://developer.apple.com/library/ios/documentation/graphicsimaging/reference/CoreImageFilterReference/Reference/reference.html#//apple_ref/doc/uid/TP40004346

Answer 3

一個更簡單的回答：如果你的圖像可以是單顏色（例如線圖），然後就指定要UIImageRenderingModeAlwaysTemplate。現在圖像將採用其容器的tintColor，因此只需更改tintColor即可更改其顏色。

Answer 4

基於Xu Yin's answer - 這更好的擬合SVG狀圖標那些在他們圓形圖案（並因此可能通過程序的原始版本像素化）的一個版本。

這個改變只是當前alpha級別對每個像素值的使用（乘法）。

- (UIImage *)useColor:(UIColor *)color forImage:(UIImage *)image { 
    if(!color) 
     return image; 

    NSUInteger width = CGImageGetWidth([image CGImage]); 
    NSUInteger height = CGImageGetHeight([image CGImage]); 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    NSUInteger bytesPerPixel = 4; 
    NSUInteger bytesPerRow = bytesPerPixel * width; 
    NSUInteger bitsPerComponent = 8; 
    NSUInteger bitmapByteCount = bytesPerRow * height; 

    unsigned char *rawData = (unsigned char*) calloc(bitmapByteCount, sizeof(unsigned char)); 

    CGContextRef context = CGBitmapContextCreate(rawData, width, height, 
               bitsPerComponent, bytesPerRow, colorSpace, 
               kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); 
    CGColorSpaceRelease(colorSpace); 

    CGContextDrawImage(context, CGRectMake(0, 0, width, height), [image CGImage]); 

    CGColorRef cgColor = [color CGColor]; 
    const CGFloat *components = CGColorGetComponents(cgColor); 
    float r = components[0] * 255.0; 
    float g = components[1] * 255.0; 
    float b = components[2] * 255.0; 

    int byteIndex = 0; 

    while (byteIndex < bitmapByteCount) { 
     int oldR = rawData[byteIndex]; 
     int oldG = rawData[byteIndex + 1]; 
     int oldB = rawData[byteIndex + 2]; 
     int oldA = rawData[byteIndex + 3]; 
     if(oldR != 0 || oldG != 0 || oldB != 0 || oldA != 0) { 
      rawData[byteIndex] = r * (oldA/255.0); 
      rawData[byteIndex + 1] = g * (oldA/255.0); 
      rawData[byteIndex + 2] = b * (oldA/255.0); 
     } 

     byteIndex += 4; 
    } 

    UIImage *result = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context) scale:image.scale orientation:image.imageOrientation]; 

    CGContextRelease(context); 
    free(rawData); 

    return result; 
}