0

我需要阅读 CAEAGLLayer 的内容，它有各种宽度和高度（基于背景图像大小）。在 iPad 模拟器上一切正常，但在设备上我有崩溃或奇怪的水平线而不是内容。宽度不会发生崩溃，例如，从 537 到 544 像素

我正在使用以下代码

- (UIImage*)image
{
        // Get the size of the backing CAEAGLLayer
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);

    NSInteger x = 0, y = 0, width = backingWidth, height = backingHeight;
    NSInteger dataLength = width * height * 4;
    GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));

        // Read pixel data from the framebuffer
    glPixelStorei(GL_PACK_ALIGNMENT, 4);
    glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);

        // Create a CGImage with the pixel data
        // If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
        // otherwise, use kCGImageAlphaPremultipliedLast
    CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
    CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
    CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
                                    ref, NULL, true, kCGRenderingIntentDefault);

        // OpenGL ES measures data in PIXELS
        // Create a graphics context with the target size measured in POINTS
    NSInteger widthInPoints, heightInPoints;
        // if (NULL != UIGraphicsBeginImageContextWithOptions) {
        // // On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
        // // Set the scale parameter to your OpenGL ES view's contentScaleFactor
        // // so that you get a high-resolution snapshot when its value is greater than 1.0
        // CGFloat scale = eaglview.contentScaleFactor;
        // widthInPoints = width / scale;
        // heightInPoints = height / scale;
        // UIGraphicsBeginImageContextWithOptions(CGSizeMake( widthInPoints, heightInPoints), NO, scale);
        // }
        // else {
        // On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
    widthInPoints = width;
    heightInPoints = height;
    UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
        // }

    CGContextRef cgcontext = UIGraphicsGetCurrentContext();

        // UIKit coordinate system is upside down to GL/Quartz coordinate system
        // Flip the CGImage by rendering it to the flipped bitmap context
        // The size of the destination area is measured in POINTS
    CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
    CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);

        // Retrieve the UIImage from the current context
    UIImage *image1 = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

        // Clean up
    free(data);
    CFRelease(ref);
    CFRelease(colorspace);
    CGImageRelease(iref);

    return image1;
}
4

2 回答 2

4

您正在读取的视图或可绘制区域必须是 32 的倍数（可能是 16，但我尚未对此进行测试）。也许您可以尝试将绘图区域的大小调整为 32 的倍数？我之前遇到了水平线问题，将我正在阅读的部分从 400x300 调整为 384x288 修复了所有问题。

于 2010-09-20T09:09:24.100 回答
0

在我的情况下，任何宽度乘以 4 都有效！

于 2010-12-15T20:18:04.630 回答