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Developer
Posts: 1,531
Registered: ‎07-14-2008
My Device: Z10
Accepted Solution

Saving bitmap to PNG loses transparent

I have a png picture as a resource file with transparency.

 

I had make some changes to the bitmap and have saved to sd card as png format but

the transparent color is black.

 

how do i save the bitmap to png with the transparent color? thanks

 

 

Developer
Posts: 16,495
Registered: ‎07-29-2008
My Device: Z10 LE, Z30, Passport

Re: Saving bitmap to PNG loses transparent

i don't think it is possible, bitmap does not support transparency.

an old workaround was to use pink (or similar) instead of the transparency and replace it at the end again, maybe you find something about this searching the web.

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Developer
Posts: 1,805
Registered: ‎04-28-2009
My Device: Z10 (STL100-4)-10.2.1.3253, Z10 (STL100-3)-10.3.1.997 Dev OS, Z30 (STA100-5)-10.3.1.997 Dev OS, Passport (SQW100-1)-10.3.0.1418, PlayBook (16GB)-2.1.0.1917

Re: Saving bitmap to PNG loses transparent

[ Edited ]

I think he means something like system.Bitmap, not bitmap the file format.

 

I did a quick search and found this:

http://supportforums.blackberry.com/t5/Java-Development/Bug-in-PNG-Encoding-Bitmap-to-PNG-with-trans...

 

Oops, just looked at the solution. Might not be helpful... What are you using to create the PNG?

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Developer
Posts: 1,531
Registered: ‎07-14-2008
My Device: Z10

Re: Saving bitmap to PNG loses transparent

thanks.

 

I have a original png file as a resource.  load it as a bitmap and then i made some changes to it and then

i encode it using encodepng and then saving the data. 

 

if i draw the modified bitmap the transparencey works but i get the black color when saving the bitmap as png.

 

 

 

Developer
Posts: 1,805
Registered: ‎04-28-2009
My Device: Z10 (STL100-4)-10.2.1.3253, Z10 (STL100-3)-10.3.1.997 Dev OS, Z30 (STA100-5)-10.3.1.997 Dev OS, Passport (SQW100-1)-10.3.0.1418, PlayBook (16GB)-2.1.0.1917

Re: Saving bitmap to PNG loses transparent

Though you'd have to do some searching, there is a PNG encoder that someone (J. David Eisenberg) wrote and it supports alpha. I wasn't able to find it in a quick search.

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Visitor
Posts: 1
Registered: ‎12-13-2010
My Device: Not Specified

Re: Saving bitmap to PNG loses transparent

[ Edited ]

This class will helps to save the image with out loss of  transparency


import java.io.ByteArrayOutputStream;
import java.io.IOException;

import net.rim.device.api.compress.ZLibOutputStream;
import net.rim.device.api.system.Bitmap;
import net.rim.device.api.util.CRC32;


public class PNGEncoder {

    /** Constant specifying that alpha channel should be encoded. */
    public static final boolean ENCODE_ALPHA = true;

    /** Constant specifying that alpha channel should not be encoded. */
    public static final boolean NO_ALPHA = false;

    /** Constants for filter (NONE) */
    public static final int FILTER_NONE = 0;

    /** Constants for filter (SUB) */
    public static final int FILTER_SUB = 1;

    /** Constants for filter (UP) */
    public static final int FILTER_UP = 2;

    /** Constants for filter (LAST) */
    public static final int FILTER_LAST = 2;
    
    /** IHDR tag. */
    protected static final byte IHDR[] = {73, 72, 68, 82};
    
    /** IDAT tag. */
    protected static final byte IDAT[] = {73, 68, 65, 84};
    
    /** IEND tag. */
    protected static final byte IEND[] = {73, 69, 78, 68};

    /** The png bytes. */
    protected byte[] pngBytes;

    /** The prior row. */
    protected byte[] priorRow;

    /** The left bytes. */
    protected byte[] leftBytes;

    /** The image. */
    protected Bitmap image;

    /** The width. */
    protected int width, height;

    /** The byte position. */
    protected int bytePos, maxPos;

    /** The CRC value. */
    protected int crcValue;

    /** Encode alpha? */
    protected boolean encodeAlpha;

    /** The filter type. */
    protected int filter;

    /** The bytes-per-pixel. */
    protected int bytesPerPixel;

    /** The compression level. */
    protected int compressionLevel;

    /**
     * Class constructor
     */
    public PNGEncoder() {
        this(null, false, FILTER_NONE, 0);
    }

    /**
     * Class constructor specifying Image to encode, with no alpha channel encoding.
     *
     * @param image A Java Image object which uses the DirectColorModel
     */
    public PNGEncoder(Bitmap image) {
        this(image, false, FILTER_NONE, 0);
    }

    /**
     * Class constructor specifying Image to encode, and whether to encode alpha.
     *
     * @param image A Java Image object which uses the DirectColorModel
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     */
    public PNGEncoder(Bitmap image, boolean encodeAlpha) {
        this(image, encodeAlpha, FILTER_NONE, 0);
    }

    /**
     * Class constructor specifying Image to encode, whether to encode alpha, and filter to use.
     *
     * @param image A Java Image object which uses the DirectColorModel
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     * @param whichFilter 0=none, 1=sub, 2=up
     */
    public PNGEncoder(Bitmap image, boolean encodeAlpha, int whichFilter) {
        this(image, encodeAlpha, whichFilter, 0);
    }


    /**
     * Class constructor specifying Image source to encode, whether to encode alpha, filter to use,
     * and compression level.
     *
     * @param image A Java Image object
     * @param encodeAlpha Encode the alpha channel? false=no; true=yes
     * @param whichFilter 0=none, 1=sub, 2=up
     * @param compLevel 0..9
     */
    public PNGEncoder(Bitmap image, boolean encodeAlpha, int whichFilter, int compLevel) {
        this.image = image;
        this.encodeAlpha = encodeAlpha;
        setFilter(whichFilter);
        if (compLevel >= 0 && compLevel <= 9) {
            this.compressionLevel = compLevel;
        }
    }

    /**
     * Set the image to be encoded
     *
     * @param image A Java Image object which uses the DirectColorModel
     */
    public void setImage(Bitmap image) {
        this.image = image;
        pngBytes = null;
    }

    /**
     * Creates an array of bytes that is the PNG equivalent of the current image, specifying
     * whether to encode alpha or not.
     *
     * @param encodeAlpha boolean false=no alpha, true=encode alpha
     * @return an array of bytes, or null if there was a problem
     */
    public byte[] encode(boolean encodeAlpha) throws IOException {
        byte[]  pngIdBytes = {-119, 80, 78, 71, 13, 10, 26, 10};

        if (image == null) {
            return null;
        }
        width = image.getWidth();
        height = image.getHeight();

        /*
         * start with an array that is big enough to hold all the pixels
         * (plus filter bytes), and an extra 200 bytes for header info
         */
        pngBytes = new byte[((width + 1) * height * 3) + 200];

        /*
         * keep track of largest byte written to the array
         */
        maxPos = 0;

        bytePos = writeBytes(pngIdBytes, 0);
        
        writeHeader();

        if (writeImageData()) {
            writeEnd();
            pngBytes = resizeByteArray(pngBytes, maxPos);
        }
        else {
            pngBytes = null;
        }
        return pngBytes;
    }

    /**
     * Creates an array of bytes that is the PNG equivalent of the current image.
     * Alpha encoding is determined by its setting in the constructor.
     *
     * @return an array of bytes, or null if there was a problem
     */
    public byte[] encode() throws IOException {
        return encode(encodeAlpha);
    }

    /**
     * Set the alpha encoding on or off.
     *
     * @param encodeAlpha  false=no, true=yes
     */
    public void setEncodeAlpha(boolean encodeAlpha) {
        this.encodeAlpha = encodeAlpha;
    }

    /**
     * Retrieve alpha encoding status.
     *
     * @return boolean false=no, true=yes
     */
    public boolean getEncodeAlpha() {
        return encodeAlpha;
    }

    /**
     * Set the filter to use
     *
     * @param whichFilter from constant list
     */
    public void setFilter(int whichFilter) {
        this.filter = FILTER_NONE;
        if (whichFilter <= FILTER_LAST) {
            this.filter = whichFilter;
        }
    }

    /**
     * Retrieve filtering scheme
     *
     * @return int (see constant list)
     */
    public int getFilter() {
        return filter;
    }

    /**
     * Set the compression level to use
     *
     * @param level 0 through 9
     */
    public void setCompressionLevel(int level) {
        if (level >= 0 && level <= 9) {
            this.compressionLevel = level;
        }
    }

    /**
     * Retrieve compression level
     *
     * @return int in range 0-9
     */
    public int getCompressionLevel() {
        return compressionLevel;
    }

    /**
     * Increase or decrease the length of a byte array.
     *
     * @param array The original array.
     * @param newLength The length you wish the new array to have.
     * @return Array of newly desired length. If shorter than the
     *         original, the trailing elements are truncated.
     */
    protected byte[] resizeByteArray(byte[] array, int newLength) {
        byte[]  newArray = new byte[newLength];
        int     oldLength = array.length;

        System.arraycopy(array, 0, newArray, 0, Math.min(oldLength, newLength));
        return newArray;
    }

    /**
     * Write an array of bytes into the pngBytes array.
     * Note: This routine has the side effect of updating
     * maxPos, the largest element written in the array.
     * The array is resized by 1000 bytes or the length
     * of the data to be written, whichever is larger.
     *
     * @param data The data to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeBytes(byte[] data, int offset) {
        maxPos = Math.max(maxPos, offset + data.length);
        if (data.length + offset > pngBytes.length) {
            pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, data.length));
        }
        System.arraycopy(data, 0, pngBytes, offset, data.length);
        return offset + data.length;
    }

    /**
     * Write an array of bytes into the pngBytes array, specifying number of bytes to write.
     * Note: This routine has the side effect of updating
     * maxPos, the largest element written in the array.
     * The array is resized by 1000 bytes or the length
     * of the data to be written, whichever is larger.
     *
     * @param data The data to be written into pngBytes.
     * @param nBytes The number of bytes to be written.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeBytes(byte[] data, int nBytes, int offset) {
        maxPos = Math.max(maxPos, offset + nBytes);
        if (nBytes + offset > pngBytes.length) {
            pngBytes = resizeByteArray(pngBytes, pngBytes.length + Math.max(1000, nBytes));
        }
        System.arraycopy(data, 0, pngBytes, offset, nBytes);
        return offset + nBytes;
    }

    /**
     * Write a two-byte integer into the pngBytes array at a given position.
     *
     * @param n The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeInt2(int n, int offset) {
        byte[] temp = {(byte) ((n >> 8) & 0xff), (byte) (n & 0xff)};
        return writeBytes(temp, offset);
    }

    /**
     * Write a four-byte integer into the pngBytes array at a given position.
     *
     * @param n The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeInt4(int n, int offset) {
        byte[] temp = {(byte) ((n >> 24) & 0xff),
                       (byte) ((n >> 16) & 0xff),
                       (byte) ((n >> 8) & 0xff),
                       (byte) (n & 0xff)};
        return writeBytes(temp, offset);
    }

    /**
     * Write a single byte into the pngBytes array at a given position.
     *
     * @param b The integer to be written into pngBytes.
     * @param offset The starting point to write to.
     * @return The next place to be written to in the pngBytes array.
     */
    protected int writeByte(int b, int offset) {
        byte[] temp = {(byte) b};
        return writeBytes(temp, offset);
    }

    /**
     * Write a PNG "IHDR" chunk into the pngBytes array.
     */
    protected void writeHeader() {
        int startPos;

        startPos = bytePos = writeInt4(13, bytePos);
        bytePos = writeBytes(IHDR, bytePos);
        width = image.getWidth();
        height = image.getHeight();
        bytePos = writeInt4(width, bytePos);
        bytePos = writeInt4(height, bytePos);
        bytePos = writeByte(8, bytePos); // bit depth
        bytePos = writeByte((encodeAlpha) ? 6 : 2, bytePos); // direct model
        bytePos = writeByte(0, bytePos); // compression method
        bytePos = writeByte(0, bytePos); // filter method
        bytePos = writeByte(0, bytePos); // no interlace
        crcValue = CRC32.update(CRC32.INITIAL_VALUE, pngBytes, startPos, bytePos - startPos);
        bytePos = writeInt4(crcValue, bytePos);
    }

    /**
     * Perform "sub" filtering on the given row.
     * Uses temporary array leftBytes to store the original values
     * of the previous pixels.  The array is 16 bytes long, which
     * will easily hold two-byte samples plus two-byte alpha.
     *
     * @param pixels The array holding the scan lines being built
     * @param startPos Starting position within pixels of bytes to be filtered.
     * @param width Width of a scanline in pixels.
     */
    protected void filterSub(byte[] pixels, int startPos, int width) {
        int i;
        int offset = bytesPerPixel;
        int actualStart = startPos + offset;
        int nBytes = width * bytesPerPixel;
        int leftInsert = offset;
        int leftExtract = 0;

        for (i = actualStart; i < startPos + nBytes; i++) {
            leftBytes[leftInsert] =  pixels[i];
            pixels[i] = (byte) ((pixels[i] - leftBytes[leftExtract]) % 256);
            leftInsert = (leftInsert + 1) % 0x0f;
            leftExtract = (leftExtract + 1) % 0x0f;
        }
    }

    /**
     * Perform "up" filtering on the given row.
     * Side effect: refills the prior row with current row
     *
     * @param pixels The array holding the scan lines being built
     * @param startPos Starting position within pixels of bytes to be filtered.
     * @param width Width of a scanline in pixels.
     */
    protected void filterUp(byte[] pixels, int startPos, int width) {
        int     i, nBytes;
        byte    currentByte;

        nBytes = width * bytesPerPixel;

        for (i = 0; i < nBytes; i++) {
            currentByte = pixels[startPos + i];
            pixels[startPos + i] = (byte) ((pixels[startPos  + i] - priorRow[i]) % 256);
            priorRow[i] = currentByte;
        }
    }

    /**
     * Write the image data into the pngBytes array.
     * This will write one or more PNG "IDAT" chunks. In order
     * to conserve memory, this method grabs as many rows as will
     * fit into 32K bytes, or the whole image; whichever is less.
     *
     *
     * @return true if no errors; false if error grabbing pixels
     */
    protected boolean writeImageData() throws IOException {
        int rowsLeft = height;  // number of rows remaining to write
        int startRow = 0;       // starting row to process this time through
        int nRows;              // how many rows to grab at a time

        byte[] scanLines;       // the scan lines to be compressed
        int scanPos;            // where we are in the scan lines
        int startPos;           // where this line's actual pixels start (used for filtering)

        byte[] compressedLines; // the resultant compressed lines
        int nCompressed;        // how big is the compressed area?
        
        bytesPerPixel = (encodeAlpha) ? 4 : 3;

        ByteArrayOutputStream outBytes = new ByteArrayOutputStream(1024);

        ZLibOutputStream compBytes = new ZLibOutputStream(outBytes);

        while (rowsLeft > 0) {
            nRows = Math.min(32767 / (width * (bytesPerPixel + 1)), rowsLeft);
            nRows = Math.max( nRows, 1 );

            int[] pixels = new int[width * nRows];

            image.getARGB(pixels, 0, width, 0, startRow, width, nRows);
            
            /*
             * Create a data chunk. scanLines adds "nRows" for
             * the filter bytes.
             */
            scanLines = new byte[width * nRows * bytesPerPixel + nRows];

            if (filter == FILTER_SUB) {
                leftBytes = new byte[16];
            }
            if (filter == FILTER_UP) {
                priorRow = new byte[width * bytesPerPixel];
            }

            scanPos = 0;
            startPos = 1;
            for (int i = 0; i < width * nRows; i++) {
                if (i % width == 0) {
                    scanLines[scanPos++] = (byte) filter;
                    startPos = scanPos;
                }
                scanLines[scanPos++] = (byte) ((pixels[i] >> 16) & 0xff);
                scanLines[scanPos++] = (byte) ((pixels[i] >>  8) & 0xff);
                scanLines[scanPos++] = (byte) ((pixels[i]) & 0xff);
                if (encodeAlpha) {
                    scanLines[scanPos++] = (byte) ((pixels[i] >> 24) & 0xff);
                }
                if ((i % width == width - 1) && (filter != FILTER_NONE)) {
                    if (filter == FILTER_SUB) {
                        filterSub(scanLines, startPos, width);
                    }
                    if (filter == FILTER_UP) {
                        filterUp(scanLines, startPos, width);
                    }
                }
            }

            /*
             * Write these lines to the output area
             */
             compBytes.write(scanLines, 0, scanPos);

            startRow += nRows;
            rowsLeft -= nRows;
        }
        compBytes.close();

        /*
         * Write the compressed bytes
         */
        compressedLines = outBytes.toByteArray();
        nCompressed = compressedLines.length;

        bytePos = writeInt4(nCompressed, bytePos);
        bytePos = writeBytes(IDAT, bytePos);
        crcValue = CRC32.update(CRC32.INITIAL_VALUE, IDAT);

        bytePos = writeBytes(compressedLines, nCompressed, bytePos);
        crcValue = CRC32.update(crcValue, compressedLines, 0, nCompressed);

        bytePos = writeInt4(crcValue, bytePos);
        return true;
    }

    /**
     * Write a PNG "IEND" chunk into the pngBytes array.
     */
    protected void writeEnd() {
        bytePos = writeInt4(0, bytePos);
        bytePos = writeBytes(IEND, bytePos);
        crcValue = CRC32.update(CRC32.INITIAL_VALUE, IEND);

        bytePos = writeInt4(crcValue, bytePos);
    }

}

Developer
Posts: 1,805
Registered: ‎04-28-2009
My Device: Z10 (STL100-4)-10.2.1.3253, Z10 (STL100-3)-10.3.1.997 Dev OS, Z30 (STA100-5)-10.3.1.997 Dev OS, Passport (SQW100-1)-10.3.0.1418, PlayBook (16GB)-2.1.0.1917

Re: Saving bitmap to PNG loses transparent

Yes that would be it. Don't forget the license agreement that goes with it:

/**
 * PNGEncoder takes a Java Image object and creates a byte string which can be saved as a PNG file.
 * The Image is presumed to use the DirectColorModel.
 *
 * <p>Thanks to Jay Denny at KeyPoint Software
 *    http://www.keypoint.com/
 * who let me develop this code on company time.</p>
 *
 * <p>You may contact me with (probably very-much-needed) improvements,
 * comments, and bug fixes at:</p>
 *
 *   <p><code>david@catcode.com</code></p>
 *
 * <p>This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.</p>
 *
 * <p>This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.</p>
 *
 * <p>You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * A copy of the GNU LGPL may be found at
 * <code>http://www.gnu.org/copyleft/lesser.html</code></p>
 *
 * @author J. David Eisenberg
 * @version 1.5, 19 Oct 2003
 *
 * CHANGES:
 * --------
 * 19-Nov-2002 : CODING STYLE CHANGES ONLY (by David Gilbert for Object Refinery Limited);
 * 19-Sep-2003 : Fix for platforms using EBCDIC (contributed by Paulo Soares);
 * 19-Oct-2003 : Change private fields to protected fields so that
 *               PNGEncoderB can inherit them (JDE)
 *                           Fixed bug with calculation of nRows
 * 08-Apr-2008 : Ported to BlackBerry (by Richard Puckett II)
 */

 L-GPL does not require you post your source code for your program so just include a reference to it.

 

Give credit where credit is due.

---Spends time in #blackberrydev on freenode (IRC)----
Three simple rules:
1. Please use the search bar before making new posts.
2. "Like" posts that you find helpful.
3. If a solution has been found for your post, mark it as solved.
--I code too much. Well, too bad.
Developer
Posts: 16,495
Registered: ‎07-29-2008
My Device: Z10 LE, Z30, Passport

Re: Saving bitmap to PNG loses transparent

it is a widespread disease here on the forums to post code without license and/or mentioning the contributor.

----------------------------------------------------------
feel free to press the like button on the right side to thank the user that helped you.
please mark posts as solved if you found a solution.
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