Question

我正在尝试使用options.inSampleSize缩放位图，但据我所知，映射就像这样

如果inSampleSize 1，则结果图片为100％
如果inSampleSize 2，则结果图片为50％
如果inSampleSize 3，则结果图片为33％
如果inSampleSize 4，则结果图片为25％
如果inSampleSize 5，则结果图片为20％

但我想要的是一个80%缩放的结果图像。我怎么做到的？

Answer 1

你能否使用Bitmap.createScaledBitmap方法？

int srcWidth = srcBitmap.getWidth();
int srcHeight = srcBitmap.getHeight();
int dstWidth = (int)(srcWidth*0.8f);
int dstHeight = (int)(srcHeight*0.8f);
Bitmap dstBitmap = Bitmap.createScaledBitmap(srcBitmap, dstWidth, dstHeight, true);

Answer 2

您可以使用此课程中的calculateSampleSize功能。它纯粹基于计算。

package com.abhan.example.util;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;

public class ScalingUtilities {

    public static Bitmap decodeResource(Resources res, int resId, int dstWidth,
            int dstHeight, ScalingLogic scalingLogic) {
        Options options = new Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(res, resId, options);
        options.inJustDecodeBounds = false;
        options.inSampleSize = calculateSampleSize(options.outWidth,
                options.outHeight, dstWidth, dstHeight, scalingLogic);
        Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId,
                options);

        return unscaledBitmap;
    }

    public static Bitmap createScaledBitmap(Bitmap unscaledBitmap,
            int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
        Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(),
                unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic);
        Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(),
                unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic);
        Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(),
                dstRect.height(), Config.ARGB_8888);
        Canvas canvas = new Canvas(scaledBitmap);
        canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(
                Paint.FILTER_BITMAP_FLAG));

        return scaledBitmap;
    }

    public static enum ScalingLogic {
        CROP, FIT
    }

    public static int calculateSampleSize(int srcWidth, int srcHeight,
            int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect > dstAspect) {
                return srcWidth / dstWidth;
            } else {
                return srcHeight / dstHeight;
            }
        } else {
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect > dstAspect) {
                return srcHeight / dstHeight;
            } else {
                return srcWidth / dstWidth;
            }
        }
    }

    public static Rect calculateSrcRect(int srcWidth, int srcHeight,
            int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.CROP) {
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect > dstAspect) {
                final int srcRectWidth = (int) (srcHeight * dstAspect);
                final int srcRectLeft = (srcWidth - srcRectWidth) / 2;
                return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth,
                        srcHeight);
            } else {
                final int srcRectHeight = (int) (srcWidth / dstAspect);
                final int scrRectTop = (int) (srcHeight - srcRectHeight) / 2;
                return new Rect(0, scrRectTop, srcWidth, scrRectTop
                        + srcRectHeight);
            }
        } else {
            return new Rect(0, 0, srcWidth, srcHeight);
        }
    }

    public static Rect calculateDstRect(int srcWidth, int srcHeight,
            int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
        if (scalingLogic == ScalingLogic.FIT) {
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect > dstAspect) {
                return new Rect(0, 0, dstWidth, (int) (dstWidth / srcAspect));
            } else {
                return new Rect(0, 0, (int) (dstHeight * srcAspect), dstHeight);
            }
        } else {
            return new Rect(0, 0, dstWidth, dstHeight);
        }
    }

}

我希望这可以帮到你。

感谢。

Answer 3

我认为你可能误解了inSampleSize的观点。它旨在节省内存。如果您只是尝试以80％的大小绘制图像，那么在将文件读入内存后，可以使用矩阵将其调整大小（或向上）。

将位图缩放到80％

3 个答案: